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How to Build a Python GUI Application With wxPython

A Graphical User Interface or GUI is a user interface that includes graphical elements that enable a person to communicate with electronic devices like computers, hand-held devices, and other appliances. It displays information using icons, menus, and graphics. They are handled with the help of a pointing device such as a mouse, trackball or a stylus.A GUI is basically an application that has windows, buttons and lots of other widgets that allows a user to interact with your application. A web browser is a common example of a GUI that has buttons, tabs, and the main window and where the content is displayed.It was developed by the Xerox Palo Alto research laboratory in the late 1970s. Today, every OS has its own GUI. Software applications make use of these and develop their own GUIs.Python contains many GUI toolkits, out which Tkinter, wxPython, and PyQt are the important ones. All these toolkits have the ability to work with Windows, macOS, and Linux with the additional quality of working on mobile phones.How to get started with wxPython?wxPython was first released in the year 1998. It is an open-source cross-platform Python GUI toolkit used as a wrapper class around a C++ library called wxWidgets. The main feature of wxPython which distinguishes itself from other toolkits like PyQt and Tkinter is that it uses actual widgets on the native platform where required. This allows the wxPython applications to look native to the operating system in which it is running.The wxPython toolkit contains a lot of core widgets along with many custom widgets which you can download from the Extra Files section of the wxPython official page.Here, there is a download of the wxPython demo package which is an application demonstrating the robustness of the widgets included with wxPython. The main advantage of this demo is that you can view it one tab and run it in another and it also allows to edit and re-run the code to observe the changes.Installing wxPythonYou will be using the latest wxPython release, wxPython 4, which is also called the wxPython’s Project Phoenix. It is a new implementation of wxPython that aims at improving the speed, maintainability, and extensibility of wxPython. The wxPython 3 and wxPython 2 were built only for Python 2. The maintainer of wxPython rejected a lot of aliases and cleaned up a lot of code to make wxPython more easy and Pythonic.If you are migrating from an older version of wxPython to wxPython 4, take a look at the following references:Classic version vs project PhoenixPhoenix Migration GuideThe Phoenix version is compatible with both Python 2.7 and Python 3. You can use pip to install wxPython 4:$ pip install wxpythonYou will get a prerequisites section on the Github page of wxPython which will provide information to install wxPython on Linux systems.You can also look into the Extras Linux section to learn about the Python wheels for both GTK2 and GTK3 versions. To install one of the wheels, use the command below:$ pip install -U -f https://extras.wxpython.org/wxPython4/extras/linux/gtk3/ubuntu-18.04/ wxPythonRemember to modify the command to match with the version of Linux.Components of GUIAs mentioned earlier, GUI is nothing but an interface that allows user interaction.Common components of the user interfaces:Main Window.Menu.Toolbar.Buttons.Text Entry.Labels.These items are generally known as widgets. wxPython supports many other common widgets and many custom widgets that are arranged in a logical manner by a developer to allow user interaction.Event LoopsA GUI works by waiting for the user to perform an action. This is known as an event. An event occurs when something is typed by the user or when the user uses their mouse to press a button or some widget while the application is in focus.The GUI toolkit runs an infinite loop called an event loop underneath the covers. The task of the event loop is to act on occurred events on the basis of what the developer has coded the application to do. The application ignores the event when it is not able to catch it.When you are programming a graphical user interface, make sure to attach the widgets to event handlers in order to make your application do something.You can also block an event loop to make the GUI unresponsive which will appear to freeze to the user. This is a special consideration for you to keep in mind while working with event loops. Launch a special thread or process whenever a GUI takes longer than a quarter of a second to launch a process.The frameworks of wxPython contain special thread-safe methods that you can use to communicate back to your application. This informs the thread is finished or given an update.How to create a Skeleton Application?An application skeleton is basically used for prototyping. It is a user interface comprising of widgets that do not contain event handlers. You just need to create the GUI and show it to the stakeholders for signing off and avoid spending time on the backend logic.An example of creating a Hello World application with Python:import wx   application = wx.App() framework = wx.Frame(parent=None, title='Hello World') framework.Show() app.MainLoop()In the example above, there are two parts of the program – wx.App and wx.Frame. The former one is wxPython’s application object which is basically required for running the GUI. It initiates the .MainLoop() which is the event loop you have learned earlier.The latter part creates a window for user interaction. It informs wxPython that the frame has no parent and its title is Hello World. If you run the code above, this is how it will look like:The application will look different if you execute it in Mac or Linux.Note: Mac users may get the following message: This program needs access to the screen. Please run with a Framework build of Python, and only when you are logged in on the main display of your Mac. If you see this message and you are not running in a virtualenv, then you need to run your application with pythonw instead of python. If you are running wxPython from within a virtualenv, then see the wxPython wiki for the solution.The minimize, maximize and exit will be included in the wx.Frame by default. However, most wxPython code will require you to make the wx.Frame as a subclass and other widgets in order to grab the full power of the toolkit.Let us rewrite the code using class:import wx   class MyFramework(wx.Frame):     def frame(self):         super().frame(parent=None, title='Hello World') self.Show()   if __name__ == '__main__':     application = wx.App()     framework = MyFramework() application.MainLoop()This code can be used as a template for your application.Widgets in wxPythonThe wxPython toolkit allows you to create rich applications from more than one hundred widgets. But it can be very daunting to choose the perfect widget from such a large number, so wxPython has included a wxPython Demo which contains a search filter which will help you to find the right widget from the list.Now, let us add a button and allow the user to enter some text by adding a text field:import wx   class MyFramework(wx.Frame):     def frame(self):         super().frame(parent=None, title='Hello World')         panel = wx.Panel(self)   self.text_ctrl = wx.TextCtrl(panel, pos=(5, 5)) my_button = wx.Button(panel, label='Press Me', pos=(5, 55))   self.Show()   if __name__ == '__main__':     application = wx.App()     framework = MyFramework() application.MainLoop()When you run the code, the application will look like this:The first widget that is recommended on Windows is wx.Panel. It makes the background color of the frame as the right shade of gray. Tab traversal is disabled without a Panel on Windows.If the panel is the sole child of the frame, it will be expanded automatically to fill the frame with itself. The next thing you need to do is to add a wx.TextCtrl to the panel. The first argument is always that which parent the widget should go to for almost all widgets. So if you are willing to keep the text control and the button on the top of the panel, it is the parent you need to specify.You also need to inform wxPython about the position of the widget. You can do it using the pos parameter. The default location is (0,0) which is actually at the upper left corner of the parent. So to change the text control, you can change the position of the frame, you can shift its left corner 5 pixels from the left(x) and 5 pixels from the top(y). Finally, you can add your button to the panel and label it. You can also set the y-coordinate to 55 to prevent the overlapping of widgets.Absolute PositioningAbsolute positioning is the technique found in most GUI toolkits by which you can provide the exact coordinates for your widget’s position.There might be situations when you need to keep track of all your widgets and relocate the widgets in case of a complex application. This can be a really difficult thing to do. However, most modern-day toolkits provide a solution for this, which we’ll study next.Sizers (Dynamic Sizing)Sizers are methods to define the control layout in dialogs in wxPython. They have the ability to create dialogs that are not dependent on the platform. They manage the positioning of the widgets and adjust them when the user resizes the application window.Some of the primary types of sizers that are commonly used are:wx.BoxSizerwx.GridSizerwx.FlexGridSizerAn example code to add wx.BoxSizer to the previous code:import wx   class MyFramework(wx.Frame):     def frame(self):         super().frame(parent=None, title='Hello World')         panel = wx.Panel(self)         my_sizer = wx.BoxSizer(wx.VERTICAL)         self.text_ctrl = wx.TextCtrl(panel) my_sizer.Add(self.text_ctrl, 0, wx.ALL | wx.EXPAND, 5)         my_button = wx.Button(panel, label='Press Me') my_sizer.Add(my_btn, 0, wx.ALL | wx.CENTER, 5)         panel.SetSizer(my_sizer)         self.Show()   if __name__ == '__main__':     application = wx.App()     framework = MyFramework() application.MainLoop() In the example above, an instance of wx.BoxSixer is created and passed to wx.VERTICAL which is actually the orientation that widgets are included in the sizer. The widgets will be added in a vertical manner from top to bottom. You can also set the BoxSizer’s orientation to wx.HORIZONTAL. In this case, the widgets are added from left to right.  You can use .Add() to a widget to a sizer which takes maximum five arguments as follows: window ( the widget )- This is the widget that is added to the sizer. proportion - It sets how much space corresponding to other widgets in the sizer will the widget should take. By default, the proportion is zero which leaves the wxPython to its original proportion. flag - It allows you to pass in multiple flags by separating them with a pipe character: |. The text control is added using wx.ALL and wx.EXPAND flags. The wx.ALL flag adds a border on all sides of the widget. On the other hand, wx.EXPAND expands the widgets as much as the sizer can be expanded. border - This parameter informs wxPython about the number of pixels of border needed around the widget.  userData - It is a rare argument that is used for resizing in case of complex applications. However, in this example, the wx.EXPAND flag is replaced with wx.CENTER to display the button in the center on-screen. When you run the code, your application will look something like this:Adding an event using wxPython Though your application looks cool, but it really does nothing. The button you have created does nothing on pressing it. Let us give the button a job:import wx   class MyFramework(wx.Frame):     def frame(self):         super().frame(parent=None, title='Hello World')         panel = wx.Panel(self)         my_sizer = wx.BoxSizer(wx.VERTICAL)         self.text_ctrl = wx.TextCtrl(panel) my_sizer.Add(self.text_ctrl, 0, wx.ALL | wx.EXPAND, 5)         my_button = wx.Button(panel, label='Press Me') my_button.Bind(wx.EVT_BUTTON, self.on_press) my_sizer.Add(my_btn, 0, wx.ALL | wx.CENTER, 5)         panel.SetSizer(my_sizer)         self.Show()   def button_press(self, event):         value = self.text_ctrl.GetValue()         if not value:             print("You didn't enter anything!")        else:             print(f'You typed: "{value}"')   if __name__ == '__main__':     application = wx.App()     framework = MyFramework() application.MainLoop() You can attach event bindings to the widgets in wxPython. This allows them to respond to certain types of events.If you want the button to do something, you can do it using the button’s .Bind() method. It takes the events you want to bind to, the handler to call an event, an optional source, and a number of optional ids. In the example above, the button object is binded to wx.EVT_BUTTON and told to call button_press when the event gets fired..button_press also accepts a second argument by convention that is called event. The event parameter suggests that the second argument should be an event object.You can get the text control’s contents with the help of GetValue() method within .button_press.How to create a Working Application?Consider a situation where you are asked to create an MP3 tag editor. The foremost thing you need to do is to look out for the required packages.Consider a situation where you are asked to create an MP3 tag editor. The foremost thing you need to do is to look out for the required packages.If you make a Google search for Python mp3 tag editor, you will find several options as below:mp3 -taggereyeD3mutagenOut of these, eyeD3 is a better choice than the other two since it has a pretty nice API that can be used without getting bogged down with MP3’s ID3 specification.You can install eyeD3 using pip from your terminal:pip install eyed3If you want to install eyeD3 in macOS, you have to install libmagic using brew. Linux and Windows users can easily install using the command mentioned above.Designing the User Interface using wxPythonThe very first thing you must do before designing an interface is to sketch out how you think the interface should look.The user interface should perform the following tasks:Open up one or more MP3 files.Display the current MP3 tags.Edit an MP3 tag.If you want to open a file or a folder, you need to have a menu or a button in your user interface. You can do that with a File menu. You will also need a widget to see the tags for multiple MP3 files. A tabular structure consisting of columns and rows would be perfect for this case since you can have labeled columns for the MP3 tags. wxPython toolkit consists of afew widgets to perform this task:wx.grid.Gridwx.ListCtrlwx.ListCtrl would be a better option of these two since the Grid widget is overkill and complex in nature. Finally, you can use a button to perform the editing tasks.Below is an illustration of what the application should look like:Creating the User Interface You can refer to a lot of approaches when you are creating a user interface. You can follow the Model-View-Controller design pattern that is used for developing user interfaces which divides the program logic into three interconnected elements. You should know how to split up classes and how many classes should be included in a single file and so on.However, in this case, you need only two classes which are as follows:wx.Panel classwx.Frame class Let’s start with imports and the panel class:import eyed3 import glob import wx   class Mp3Panel(wx.Panel):     def frame(self, parent):         super().__init__(parent) main_sizer = wx.BoxSizer(wx.VERTICAL) self.row_obj_dict = {}   self.list_ctrl = wx.ListCtrl(             self, size=(-1, 100),               style=wx.LC_REPORT | wx.BORDER_SUNKEN         ) self.list_ctrl.InsertColumn(0, 'Artist', width=140) self.list_ctrl.InsertColumn(1, 'Album', width=140) self.list_ctrl.InsertColumn(2, 'Title', width=200) main_sizer.Add(self.list_ctrl, 0, wx.ALL | wx.EXPAND, 0)         edit_button = wx.Button(self, label='Edit') edit_button.Bind(wx.EVT_BUTTON, self.on_edit) main_sizer.Add(edit_button, 0, wx.ALL | wx.CENTER, 5)         self.SetSizer(main_sizer)   def on_edit(self, event):         print('in on_edit')   def update_mp3_listing(self, folder_path):         print(folder_path)In this example above, the eyed3 package, glob package, and the wx package are imported. Then, the user interface is created by making wx.Panel a subclass. A dictionary row_obj_dict is created for storing data about the MP3s. The next thing you do is create a wx.ListCtrl and set it to report mode, i.e. wx.LC_REPORT. This report flag is the most popular among all but you can also choose your own depending upon the style flag that you pass in. Now you need to call .InsertColumn() to make the ListCtrl have the correct headers and then provide the index of the column, its label and the width of the column pixels. Finally, you need to add your Edit button, an event handler, and a method. The code for the frame is as follows:class Mp3Frame(wx.Frame):     def__init__(self):         super().__init__(parent=None,                          title='Mp3 Tag Editor') self.panel = Mp3Panel(self) self.Show()   if __name__ == '__main__':     app = wx.App(False)     frame = Mp3Frame() app.MainLoop()This class function is a better and simpler approach than the previous one because you just need to set the title of the frame and instantiate the panel class, MP3Panel. The user interface will look like this after all the implementations:The next thing we will do is add a File menu to add MP3s to the application and also edit their tags.Make a Functioning ApplicationThe very first thing you need to do to make your application work is to update the wx.Frame class to include the File menu which will allow you to add MP3 files.Code to add a menu bar to our application:class Mp3Frame(wx.Frame):   def__init__(self):         wx.Frame.__init__(self, parent=None,                             title='Mp3 Tag Editor') self.panel = Mp3Panel(self) self.create_menu() self.Show()   def create_menu(self): menu_bar = wx.MenuBar() file_menu = wx.Menu() open_folder_menu_item = file_menu.Append( wx.ID_ANY, 'Open Folder',   'Open a folder with MP3s'         ) menu_bar.Append(file_menu, '&File') self.Bind(             event=wx.EVT_MENU,               handler=self.on_open_folder,             source=open_folder_menu_item,         ) self.SetMenuBar(menu_bar)   def on_open_folder(self, event):         title = "Choose a directory:" dlg = wx.DirDialog(self, title,                              style=wx.DD_DEFAULT_STYLE) if dlg.ShowModal() == wx.ID_OK:             self.panel.update_mp3_listing(dlg.GetPath()) dlg.Destroy() In the example code above, .create_menu() is called within the class’s constructor and then two instances – wx.MenuBar and wx.Menu are created.Now, if you’re willing to add an item to the menu, you need to call the menu instance’s .Append() and pass the following things:A unique identifierLabelA help stringAfter that call the menubar’s .Append() to add the menu to the menubar. It will take the menu instance and the label for menu. The label is called as &File so that a keyboard shortcut is created to open the File menu using just the keyboard.Now self.Bind() is called to bind the frame to wx.EVT_MENU. This informs wxPython about which handler should be used and which source to bind the handler to. Lastly, call the frame’s .SetMenuBar and pass it the menubar instance. Your menu is now added to the frame.Now let’s come back to the menu item’s event handler:def on_open_folder(self, event):     title = "Choose a directory:" dlg = wx.DirDialog(self, title, style=wx.DD_DEFAULT_STYLE) if dlg.ShowModal() == wx.ID_OK:         self.panel.update_mp3_listing(dlg.GetPath()) dlg.Destroy()You can use wxPython’s wx.DirDialog to choose the directories of the correct MP3 folder. To display the dialog, use .ShowModal(). This will display the dialog modally but will disallow the user to interact with the main application.  You can get to the user’s choice of path using .GetPath() whenever the user presses the OK button. This path has to be added to the panel class and this can be done by the panel’s .update_mp3_listing().Finally, you will have to close the dialog and the best method is using .Destroy().  There are methods to close the dialog like .Close() which will just dialog but will not destroy it, so .Destroy() is the most effective option to prevent such situation.Now let’s update the MP3Panel class starting with .update_mp3_listing():def update_mp3_listing(self, folder_path): self.current_folder_path = folder_path self.list_ctrl.ClearAll()   self.list_ctrl.InsertColumn(0, 'Artist', width=140) self.list_ctrl.InsertColumn(1, 'Album', width=140) self.list_ctrl.InsertColumn(2, 'Title', width=200) self.list_ctrl.InsertColumn(3, 'Year', width=200)       mp3s = glob.glob(folder_path + '/*.mp3')     mp3_objects = []     index = 0 for mp3 in mp3s:         mp3_object = eyed3.load(mp3) self.list_ctrl.InsertItem(index,               mp3_object.tag.artist) self.list_ctrl.SetItem(index, 1,               mp3_object.tag.album) self.list_ctrl.SetItem(index, 2,               mp3_object.tag.title)         mp3_objects.append(mp3_object) self.row_obj_dict[index] = mp3_object         index += 1In the example above, the current directory is set to the specified folder and the list control is cleared. The list controls stay fresh and shows the MP3s you’re currently working with. Next, the folder is taken and Python’s globmoduleis used to search for the MP3 files. Then, the MP3s are looped over and converted into eyed3 objects. This is done by calling the .load() of eyed3. After that, you can add the artist, album, and the title of the Mp3 to the control list given that the MP3s have the appropriate tags..InsertItem() is used to add a new row to a list control for the first time and SetItem()  is used to add rows to the subsequent columns. The last step is to save your MP3 object to your Python dictionary row_obj_dict.Now to edit an MP3’s tags, you need to update the .on_edit() event handler:def on_edit(self, event):     selection = self.list_ctrl.GetFocusedItem() if selection >= 0:         mp3 = self.row_obj_dict[selection] dlg = EditDialog(mp3) dlg.ShowModal()         self.update_mp3_listing(self.current_folder_path) dlg.Destroy()The user’s selection is taken by calling the list control’s .GetFocusedItem(). It will return -1 if the user will not select anything in the list control. However, if you want to extract the MP3 obj3ct from the dictionary, the user have to select something. You can then open the MP3 tag editor dialog which will be a custom dialog. As before, the dialog is shown modally, then the last two lines in .on_edit() will execute what will eventually display the current MP3 tag information. SummaryLet us sum up what we have learned in this article so far – Installing wxPython and Working with wxPython’s widgets Working of events in wxPython Comparing absolute positioning with sizers Creating a skeleton application and a working application The main feature of the wxPython Graphical User Interface is its robustness and a large collection of widgets that you can use to build cross-platform applications. Since you have now learned how to create a working application, that is an MP3 tag editor, you can try your hand to enhance this application to a more beautiful one with lots of new features or you can perhaps create your own wonderful application. To gain more knowledge about Python tips and tricks, check our Python tutorial and get a good hold over coding in Python by joining the Python certification course.
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How to Build a Python GUI Application With wxPython

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How to Build a Python GUI Application With wxPython

A Graphical User Interface or GUI is a user interface that includes graphical elements that enable a person to communicate with electronic devices like computers, hand-held devices, and other appliances. It displays information using icons, menus, and graphics. They are handled with the help of a pointing device such as a mouse, trackball or a stylus.

A GUI is basically an application that has windows, buttons and lots of other widgets that allows a user to interact with your application. A web browser is a common example of a GUI that has buttons, tabs, and the main window and where the content is displayed.

It was developed by the Xerox Palo Alto research laboratory in the late 1970s. Today, every OS has its own GUI. Software applications make use of these and develop their own GUIs.

Python contains many GUI toolkits, out which Tkinter, wxPython, and PyQt are the important ones. All these toolkits have the ability to work with Windows, macOS, and Linux with the additional quality of working on mobile phones.

How to get started with wxPython?

wxPython was first released in the year 1998. It is an open-source cross-platform Python GUI toolkit used as a wrapper class around a C++ library called wxWidgets. The main feature of wxPython which distinguishes itself from other toolkits like PyQt and Tkinter is that it uses actual widgets on the native platform where required. This allows the wxPython applications to look native to the operating system in which it is running.

The wxPython toolkit contains a lot of core widgets along with many custom widgets which you can download from the Extra Files section of the wxPython official page.

Here, there is a download of the wxPython demo package which is an application demonstrating the robustness of the widgets included with wxPython. The main advantage of this demo is that you can view it one tab and run it in another and it also allows to edit and re-run the code to observe the changes.

Installing wxPython

You will be using the latest wxPython release, wxPython 4, which is also called the wxPython’s Project Phoenix. It is a new implementation of wxPython that aims at improving the speed, maintainability, and extensibility of wxPython. The wxPython 3 and wxPython 2 were built only for Python 2. The maintainer of wxPython rejected a lot of aliases and cleaned up a lot of code to make wxPython more easy and Pythonic.

If you are migrating from an older version of wxPython to wxPython 4, take a look at the following references:

The Phoenix version is compatible with both Python 2.7 and Python 3. You can use pip to install wxPython 4:

$ pip install wxpython

You will get a prerequisites section on the Github page of wxPython which will provide information to install wxPython on Linux systems.

You can also look into the Extras Linux section to learn about the Python wheels for both GTK2 and GTK3 versions. To install one of the wheels, use the command below:

$ pip install -U -f https://extras.wxpython.org/wxPython4/extras/linux/gtk3/ubuntu-18.04/ wxPython

Remember to modify the command to match with the version of Linux.

Components of GUI

As mentioned earlier, GUI is nothing but an interface that allows user interaction.

Common components of the user interfaces:

  • Main Window.
  • Menu.
  • Toolbar.
  • Buttons.
  • Text Entry.
  • Labels.

These items are generally known as widgets. wxPython supports many other common widgets and many custom widgets that are arranged in a logical manner by a developer to allow user interaction.

Event Loops

A GUI works by waiting for the user to perform an action. This is known as an event. An event occurs when something is typed by the user or when the user uses their mouse to press a button or some widget while the application is in focus.

The GUI toolkit runs an infinite loop called an event loop underneath the covers. The task of the event loop is to act on occurred events on the basis of what the developer has coded the application to do. The application ignores the event when it is not able to catch it.

When you are programming a graphical user interface, make sure to attach the widgets to event handlers in order to make your application do something.

You can also block an event loop to make the GUI unresponsive which will appear to freeze to the user. This is a special consideration for you to keep in mind while working with event loops. Launch a special thread or process whenever a GUI takes longer than a quarter of a second to launch a process.

The frameworks of wxPython contain special thread-safe methods that you can use to communicate back to your application. This informs the thread is finished or given an update.

How to create a Skeleton Application?

An application skeleton is basically used for prototyping. It is a user interface comprising of widgets that do not contain event handlers. You just need to create the GUI and show it to the stakeholders for signing off and avoid spending time on the backend logic.

An example of creating a Hello World application with Python:

import wx
 
application = wx.App()
framework = wx.Frame(parent=None, title='Hello World')
framework.Show()
app.MainLoop()

In the example above, there are two parts of the program – wx.App and wx.Frame. The former one is wxPython’s application object which is basically required for running the GUI. It initiates the .MainLoop() which is the event loop you have learned earlier.

The latter part creates a window for user interaction. It informs wxPython that the frame has no parent and its title is Hello World. If you run the code above, this is how it will look like:

How to create a Skeleton Application in Python

The application will look different if you execute it in Mac or Linux.

Note: Mac users may get the following message: This program needs access to the screen. Please run with a Framework build of Python, and only when you are logged in on the main display of your Mac. If you see this message and you are not running in a virtualenv, then you need to run your application with pythonw instead of python. If you are running wxPython from within a virtualenv, then see the wxPython wiki for the solution.

The minimize, maximize and exit will be included in the wx.Frame by default. However, most wxPython code will require you to make the wx.Frame as a subclass and other widgets in order to grab the full power of the toolkit.

Let us rewrite the code using class:

import wx
 
class MyFramework(wx.Frame):    
def frame(self):
        super().frame(parent=None, title='Hello World')
self.Show()
 
if __name__ == '__main__':
    application = wx.App()
    framework = MyFramework()
application.MainLoop()

This code can be used as a template for your application.

Widgets in wxPython

The wxPython toolkit allows you to create rich applications from more than one hundred widgets. But it can be very daunting to choose the perfect widget from such a large number, so wxPython has included a wxPython Demo which contains a search filter which will help you to find the right widget from the list.

Now, let us add a button and allow the user to enter some text by adding a text field:

import wx
 
class MyFramework(wx.Frame):    
def frame(self):
        super().frame(parent=None, title='Hello World')
        panel = wx.Panel(self)
 
self.text_ctrl = wx.TextCtrl(panel, pos=(5, 5))
my_button = wx.Button(panel, label='Press Me', pos=(5, 55))
 
self.Show()
 
if __name__ == '__main__':
    application = wx.App()
    framework = MyFramework()
application.MainLoop()

When you run the code, the application will look like this:

The first widget that is recommended on Windows is wx.Panel. It makes the background color of the frame as the right shade of gray. Tab traversal is disabled without a Panel on Windows.

If the panel is the sole child of the frame, it will be expanded automatically to fill the frame with itself. The next thing you need to do is to add a wx.TextCtrl to the panel. The first argument is always that which parent the widget should go to for almost all widgets. So if you are willing to keep the text control and the button on the top of the panel, it is the parent you need to specify.

You also need to inform wxPython about the position of the widget. You can do it using the pos parameter. The default location is (0,0) which is actually at the upper left corner of the parent. So to change the text control, you can change the position of the frame, you can shift its left corner 5 pixels from the left(x) and 5 pixels from the top(y). Finally, you can add your button to the panel and label it. You can also set the y-coordinate to 55 to prevent the overlapping of widgets.

Absolute Positioning

Absolute positioning is the technique found in most GUI toolkits by which you can provide the exact coordinates for your widget’s position.

There might be situations when you need to keep track of all your widgets and relocate the widgets in case of a complex application. This can be a really difficult thing to do. However, most modern-day toolkits provide a solution for this, which we’ll study next.

Sizers (Dynamic Sizing)

Sizers are methods to define the control layout in dialogs in wxPython. They have the ability to create dialogs that are not dependent on the platform. They manage the positioning of the widgets and adjust them when the user resizes the application window.

Some of the primary types of sizers that are commonly used are:

  • wx.BoxSizer
  • wx.GridSizer
  • wx.FlexGridSizer

An example code to add wx.BoxSizer to the previous code:

import wx
 
class MyFramework(wx.Frame):    
def frame(self):
        super().frame(parent=None, title='Hello World')
        panel = wx.Panel(self)        
my_sizer = wx.BoxSizer(wx.VERTICAL)        
self.text_ctrl = wx.TextCtrl(panel)
my_sizer.Add(self.text_ctrl, 0, wx.ALL | wx.EXPAND, 5)        
my_button = wx.Button(panel, label='Press Me')
my_sizer.Add(my_btn, 0, wx.ALL | wx.CENTER, 5)        
panel.SetSizer(my_sizer)        
self.Show()
 
if __name__ == '__main__':
    application = wx.App()
    framework = MyFramework()
application.MainLoop() 

In the example above, an instance of wx.BoxSixer is created and passed to wx.VERTICAL which is actually the orientation that widgets are included in the sizer. The widgets will be added in a vertical manner from top to bottom. You can also set the BoxSizer’s orientation to wx.HORIZONTAL. In this case, the widgets are added from left to right.  

You can use .Add() to a widget to a sizer which takes maximum five arguments as follows: 

  • window ( the widget )- This is the widget that is added to the sizer. 
  • proportion - It sets how much space corresponding to other widgets in the sizer will the widget should take. By default, the proportion is zero which leaves the wxPython to its original proportion. 
  • flag - It allows you to pass in multiple flags by separating them with a pipe character: |. The text control is added using wx.ALL and wx.EXPAND flags. The wx.ALL flag adds a border on all sides of the widget. On the other hand, wx.EXPAND expands the widgets as much as the sizer can be expanded. 
  • border - This parameter informs wxPython about the number of pixels of border needed around the widget.  
  • userData - It is a rare argument that is used for resizing in case of complex applications. 

However, in this example, the wx.EXPAND flag is replaced with wx.CENTER to display the button in the center on-screen. 

When you run the code, your application will look something like this:

Run code of python

Adding an event using wxPython 

Though your application looks cool, but it really does nothing. The button you have created does nothing on pressing it. Let us give the button a job:

import wx
 
class MyFramework(wx.Frame):    
def frame(self):
        super().frame(parent=None, title='Hello World')
        panel = wx.Panel(self)        
my_sizer = wx.BoxSizer(wx.VERTICAL)        
self.text_ctrl = wx.TextCtrl(panel)
my_sizer.Add(self.text_ctrl, 0, wx.ALL | wx.EXPAND, 5)        
my_button = wx.Button(panel, label='Press Me')
my_button.Bind(wx.EVT_BUTTON, self.on_press)
my_sizer.Add(my_btn, 0, wx.ALL | wx.CENTER, 5)        
panel.SetSizer(my_sizer)        
self.Show()
 
def button_press(self, event):
        value = self.text_ctrl.GetValue()
        if not value:
            print("You didn't enter anything!")
       else:
            print(f'You typed: "{value}"')
 
if __name__ == '__main__':
    application = wx.App()
    framework = MyFramework()
application.MainLoop() 

You can attach event bindings to the widgets in wxPython. This allows them to respond to certain types of events.

If you want the button to do something, you can do it using the button’s .Bind() method. It takes the events you want to bind to, the handler to call an event, an optional source, and a number of optional ids. In the example above, the button object is binded to wx.EVT_BUTTON and told to call button_press when the event gets fired.

.button_press also accepts a second argument by convention that is called event. The event parameter suggests that the second argument should be an event object.

You can get the text control’s contents with the help of GetValue() method within .button_press.

How to create a Working Application?

Consider a situation where you are asked to create an MP3 tag editor. The foremost thing you need to do is to look out for the required packages.

Consider a situation where you are asked to create an MP3 tag editor. The foremost thing you need to do is to look out for the required packages.

If you make a Google search for Python mp3 tag editor, you will find several options as below:

  • mp3 -tagger
  • eyeD3
  • mutagen

Out of these, eyeD3 is a better choice than the other two since it has a pretty nice API that can be used without getting bogged down with MP3’s ID3 specification.

You can install eyeD3 using pip from your terminal:

pip install eyed3

If you want to install eyeD3 in macOS, you have to install libmagic using brew. Linux and Windows users can easily install using the command mentioned above.

Designing the User Interface using wxPython

The very first thing you must do before designing an interface is to sketch out how you think the interface should look.

The user interface should perform the following tasks:

  • Open up one or more MP3 files.
  • Display the current MP3 tags.
  • Edit an MP3 tag.

If you want to open a file or a folder, you need to have a menu or a button in your user interface. You can do that with a File menu. You will also need a widget to see the tags for multiple MP3 files. A tabular structure consisting of columns and rows would be perfect for this case since you can have labeled columns for the MP3 tags. wxPython toolkit consists of afew widgets to perform this task:

  • wx.grid.Grid
  • wx.ListCtrl

wx.ListCtrl would be a better option of these two since the Grid widget is overkill and complex in nature. Finally, you can use a button to perform the editing tasks.

Below is an illustration of what the application should look like:

MP3 Tog Editor

Creating the User Interface 

You can refer to a lot of approaches when you are creating a user interface. You can follow the Model-View-Controller design pattern that is used for developing user interfaces which divides the program logic into three interconnected elements. You should know how to split up classes and how many classes should be included in a single file and so on.

However, in this case, you need only two classes which are as follows:

  • wx.Panel class
  • wx.Frame class

 Let’s start with imports and the panel class:

import eyed3
import glob
import wx
 
class Mp3Panel(wx.Panel):    
def frame(self, parent):
        super().__init__(parent)
main_sizer = wx.BoxSizer(wx.VERTICAL)
self.row_obj_dict = {}
 
self.list_ctrl = wx.ListCtrl(
            self, size=(-1, 100),  
            style=wx.LC_REPORT | wx.BORDER_SUNKEN
        )
self.list_ctrl.InsertColumn(0, 'Artist', width=140)
self.list_ctrl.InsertColumn(1, 'Album', width=140)
self.list_ctrl.InsertColumn(2, 'Title', width=200)
main_sizer.Add(self.list_ctrl, 0, wx.ALL | wx.EXPAND, 0)        
edit_button = wx.Button(self, label='Edit')
edit_button.Bind(wx.EVT_BUTTON, self.on_edit)
main_sizer.Add(edit_button, 0, wx.ALL | wx.CENTER, 5)        
self.SetSizer(main_sizer)
 
def on_edit(self, event):
        print('in on_edit')
 
def update_mp3_listing(self, folder_path):
        print(folder_path)

In this example above, the eyed3 package, glob package, and the wx package are imported. Then, the user interface is created by making wx.Panel a subclass. A dictionary row_obj_dict is created for storing data about the MP3s. 

The next thing you do is create a wx.ListCtrl and set it to report mode, i.e. wx.LC_REPORT. This report flag is the most popular among all but you can also choose your own depending upon the style flag that you pass in. Now you need to call .InsertColumn() to make the ListCtrl have the correct headers and then provide the index of the column, its label and the width of the column pixels. 

Finally, you need to add your Edit button, an event handler, and a method. The code for the frame is as follows:

class Mp3Frame(wx.Frame):    
def__init__(self):
        super().__init__(parent=None,
                         title='Mp3 Tag Editor')
self.panel = Mp3Panel(self)
self.Show()
 
if __name__ == '__main__':
    app = wx.App(False)
    frame = Mp3Frame()
app.MainLoop()

This class function is a better and simpler approach than the previous one because you just need to set the title of the frame and instantiate the panel class, MP3Panel. The user interface will look like this after all the implementations:

The next thing we will do is add a File menu to add MP3s to the application and also edit their tags.

Make a Functioning Application

The very first thing you need to do to make your application work is to update the wx.Frame class to include the File menu which will allow you to add MP3 files.

Code to add a menu bar to our application:

class Mp3Frame(wx.Frame):
 
def__init__(self):
        wx.Frame.__init__(self, parent=None,  
                          title='Mp3 Tag Editor')
self.panel = Mp3Panel(self)
self.create_menu()
self.Show()
 
def create_menu(self):
menu_bar = wx.MenuBar()
file_menu = wx.Menu()
open_folder_menu_item = file_menu.Append(
wx.ID_ANY, 'Open Folder',  
'Open a folder with MP3s'
        )
menu_bar.Append(file_menu, '&File')
self.Bind(
            event=wx.EVT_MENU,  
            handler=self.on_open_folder,
            source=open_folder_menu_item,
        )
self.SetMenuBar(menu_bar)
 
def on_open_folder(self, event):
        title = "Choose a directory:"
dlg = wx.DirDialog(self, title,  
                           style=wx.DD_DEFAULT_STYLE)
if dlg.ShowModal() == wx.ID_OK:
            self.panel.update_mp3_listing(dlg.GetPath())
dlg.Destroy() 

In the example code above, .create_menu() is called within the class’s constructor and then two instances – wx.MenuBar and wx.Menu are created.

Now, if you’re willing to add an item to the menu, you need to call the menu instance’s .Append() and pass the following things:

  • A unique identifier
  • Label
  • A help string

After that call the menubar’s .Append() to add the menu to the menubar. It will take the menu instance and the label for menu. The label is called as &File so that a keyboard shortcut is created to open the File menu using just the keyboard.

Now self.Bind() is called to bind the frame to wx.EVT_MENU. This informs wxPython about which handler should be used and which source to bind the handler to. Lastly, call the frame’s .SetMenuBar and pass it the menubar instance. Your menu is now added to the frame.

Now let’s come back to the menu item’s event handler:

def on_open_folder(self, event):
    title = "Choose a directory:"
dlg = wx.DirDialog(self, title, style=wx.DD_DEFAULT_STYLE)
if dlg.ShowModal() == wx.ID_OK:
        self.panel.update_mp3_listing(dlg.GetPath())
dlg.Destroy()

You can use wxPython’s wx.DirDialog to choose the directories of the correct MP3 folder. To display the dialog, use .ShowModal(). This will display the dialog modally but will disallow the user to interact with the main application.  You can get to the user’s choice of path using .GetPath() whenever the user presses the OK button. This path has to be added to the panel class and this can be done by the panel’s .update_mp3_listing().

Finally, you will have to close the dialog and the best method is using .Destroy().  There are methods to close the dialog like .Close() which will just dialog but will not destroy it, so .Destroy() is the most effective option to prevent such situation.

Now let’s update the MP3Panel class starting with .update_mp3_listing():

def update_mp3_listing(self, folder_path):
self.current_folder_path = folder_path
self.list_ctrl.ClearAll()
 
self.list_ctrl.InsertColumn(0, 'Artist', width=140)
self.list_ctrl.InsertColumn(1, 'Album', width=140)
self.list_ctrl.InsertColumn(2, 'Title', width=200)
self.list_ctrl.InsertColumn(3, 'Year', width=200)
 
    mp3s = glob.glob(folder_path + '/*.mp3')
    mp3_objects = []
    index = 0
for mp3 in mp3s:
        mp3_object = eyed3.load(mp3)
self.list_ctrl.InsertItem(index,  
            mp3_object.tag.artist)
self.list_ctrl.SetItem(index, 1,  
            mp3_object.tag.album)
self.list_ctrl.SetItem(index, 2,  
            mp3_object.tag.title)
        mp3_objects.append(mp3_object)
self.row_obj_dict[index] = mp3_object
        index += 1

In the example above, the current directory is set to the specified folder and the list control is cleared. The list controls stay fresh and shows the MP3s you’re currently working with. Next, the folder is taken and Python’s globmoduleis used to search for the MP3 files. Then, the MP3s are looped over and converted into eyed3 objects. This is done by calling the .load() of eyed3. After that, you can add the artist, album, and the title of the Mp3 to the control list given that the MP3s have the appropriate tags.

.InsertItem() is used to add a new row to a list control for the first time and SetItem()  is used to add rows to the subsequent columns. The last step is to save your MP3 object to your Python dictionary row_obj_dict.

Now to edit an MP3’s tags, you need to update the .on_edit() event handler:

def on_edit(self, event):
    selection = self.list_ctrl.GetFocusedItem()
if selection >= 0:
        mp3 = self.row_obj_dict[selection]
        dlg = EditDialog(mp3)
        dlg.ShowModal()
        self.update_mp3_listing(self.current_folder_path)
        dlg.Destroy()

The user’s selection is taken by calling the list control’s .GetFocusedItem(). It will return -1 if the user will not select anything in the list control. However, if you want to extract the MP3 obj3ct from the dictionary, the user have to select something. You can then open the MP3 tag editor dialog which will be a custom dialog. 

As before, the dialog is shown modally, then the last two lines in .on_edit() will execute what will eventually display the current MP3 tag information. 

Summary

Let us sum up what we have learned in this article so far – 

  • Installing wxPython and Working with wxPython’s widgets 
  • Working of events in wxPython 
  • Comparing absolute positioning with sizers 
  • Creating a skeleton application and a working application 

The main feature of the wxPython Graphical User Interface is its robustness and a large collection of widgets that you can use to build cross-platform applications. Since you have now learned how to create a working application, that is an MP3 tag editor, you can try your hand to enhance this application to a more beautiful one with lots of new features or you can perhaps create your own wonderful application. To gain more knowledge about Python tips and tricks, check our Python tutorial and get a good hold over coding in Python by joining the Python certification course.

Priyankur

Priyankur Sarkar

Data Science Enthusiast

Priyankur Sarkar loves to play with data and get insightful results out of it, then turn those data insights and results in business growth. He is an electronics engineer with a versatile experience as an individual contributor and leading teams, and has actively worked towards building Machine Learning capabilities for organizations.

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Here, there are four cases to consider:If n is positive and d >= 5, round upIf n is positive and d < 5, round downIf n is negative and d >= 5, round downIf n is negative and d < 5, round upAfter rounding as per the rules mentioned above, you can shift the decimal place back to the left.There is a question which might come to your mind - How do you handle situations where the number of positive and negative ties are drastically different? The answer to this question brings us full circle to the function that deceived us at the beginning of this article: Python’s built-in  round() function.Rounding Half To EvenThere is a way to mitigate rounding bias while you are rounding values in a dataset. You can simply round ties to the nearest even number at the desired precision. Let us look at some examples:ValueRound Half To Even ToResult16.255Tens place2016.255Ones place1616.255Tenths place16.216.255Hundredths place16.26To prove that round() really does round to even, let us try on a few different values:>>> round(4.5) 4 >>> round(3.5) 4 >>> round(1.75, 1) 1.8 >>> round(1.65, 1) 1.6The Decimal ClassThe  decimal module in Python is one of those features of the language which you might not be aware of if you have just started learning Python. Decimal “is based on a floating-point model which was designed with people in mind, and necessarily has a paramount guiding principle – computers must provide an arithmetic that works in the same way as the arithmetic that people learn at school.” – except from the decimal arithmetic specification. Some of the benefits of the decimal module are mentioned below -Exact decimal representation: 0.1 is actually 0.1, and 0.1 + 0.1 + 0.1 - 0.3 returns 0, as expected.Preservation of significant digits: When you add 1.50 and 2.30, the result is 3.80 with the trailing zero maintained to indicate significance.User-alterable precision: The default precision of the decimal module is twenty-eight digits, but this value can be altered by the user to match the problem at hand.Let us see how rounding works in the decimal module.>>> import decimal >>> decimal.getcontext() Context(     prec=28,     rounding=ROUND_HALF_EVEN,     Emin=-999999,     Emax=999999,     capitals=1,     clamp=0,     flags=[],     traps=[         InvalidOperation,         DivisionByZero,         Overflow     ] )The function decimal.getcontext() returns a context object which represents the default context of the decimal module. It also includes the default precision and the default rounding strategy.In the above example, you will see that the default rounding strategy for the decimal module is ROUND_HALF_EVEN. It allows to align with the built-in round() functionLet us create a new Decimal instance by passing a string containing the desired value and declare a number using the decimal module’s Decimal class.>>> from decimal import Decimal >>> Decimal("0.1") Decimal('0.1')You may create a Decimal instance from a floating-point number but in that case, a floating-point representation error will be introduced. For example, this is what happens when you create a Decimal instance from the floating-point number 0.1>>> Decimal(0.1) Decimal('0.1000000000000000055511151231257827021181583404541015625')You may create Decimal instances from strings containing the decimal numbers you need in order to maintain exact precision.Rounding a Decimal using the .quantize() method:>>> Decimal("1.85").quantize(Decimal("1.0")) Decimal('1.8')The Decimal("1.0") argument in .quantize() allows to determine the number of decimal places in order to round the number. As 1.0 has one decimal place, the number 1.85 rounds to a single decimal place. Rounding half to even is the default strategy, hence the result is 1.8.Decimal class:>>> Decimal("2.775").quantize(Decimal("1.00")) Decimal('2.78')Decimal module provides another benefit. After performing arithmetic the rounding is taken care of automatically and also the significant digits are preserved.>>> decimal.getcontext().prec = 2 >>> Decimal("2.23") + Decimal("1.12") Decimal('3.4')To change the default rounding strategy, you can set the decimal.getcontect().rounding property to any one of several  flags. The following table summarizes these flags and which rounding strategy they implement:FlagRounding Strategydecimal.ROUND_CEILINGRounding updecimal.ROUND_FLOORRounding downdecimal.ROUND_DOWNTruncationdecimal.ROUND_UPRounding away from zerodecimal.ROUND_HALF_UPRounding half away from zerodecimal.ROUND_HALF_DOWNRounding half towards zerodecimal.ROUND_HALF_EVENRounding half to evendecimal.ROUND_05UPRounding up and rounding towards zeroRounding NumPy ArraysIn Data Science and scientific computation, most of the times we store data as a  NumPy array. One of the most powerful features of NumPy is the use of  vectorization and broadcasting to apply operations to an entire array at once instead of one element at a time.Let’s generate some data by creating a 3×4 NumPy array of pseudo-random numbers:>>> import numpy as np >>> np.random.seed(444) >>> data = np.random.randn(3, 4) >>> data array([[ 0.35743992,  0.3775384 ,  1.38233789,  1.17554883],        [-0.9392757 , -1.14315015, -0.54243951, -0.54870808], [ 0.20851975, 0.21268956, 1.26802054, -0.80730293]])Here, first we seed the np.random module to reproduce the output easily. Then a 3×4 NumPy array of floating-point numbers is created with np.random.randn().Do not forget to install pip3 before executing the code mentioned above. If you are using  Anaconda you are good to go.To round all of the values in the data array, pass data as the argument to the  np.around() function. The desired number of decimal places is set with the decimals keyword argument. In this case, round half to even strategy is used similar to Python’s built-in round() function.To round the data in your array to integers, NumPy offers several options which are mentioned below:numpy.ceil()numpy.floor()numpy.trunc()numpy.rint()The np.ceil() function rounds every value in the array to the nearest integer greater than or equal to the original value:>>> np.ceil(data) array([[ 1.,  1.,  2.,  2.],        [-0., -1., -0., -0.], [ 1., 1., 2., -0.]])Look at the code carefully, we have a new number! Negative zero! Let us now take a look at Pandas library, widely used in Data Science with Python.Rounding Pandas Series and DataFramePandas has been a game-changer for data analytics and data science. The two main data structures in Pandas are Dataframe and Series. Dataframe works like an Excel spreadsheet whereas you can consider Series to be columns in a spreadsheet. Series.round() and DataFrame.round() methods. Let us look at an example.Do not forget to install pip3 before executing the code mentioned above. If you are using  Anaconda you are good to go.>>> import pandas as pd >>> # Re-seed np.random if you closed your REPL since the last example >>> np.random.seed(444) >>> series = pd.Series(np.random.randn(4)) >>> series 0    0.357440 1    0.377538 2    1.382338 3    1.175549 dtype: float64 >>> series.round(2) 0    0.36 1    0.38 2    1.38 3    1.18 dtype: float64 >>> df = pd.DataFrame(np.random.randn(3, 3), columns=["A", "B", "C"]) >>> df           A         B         C 0 -0.939276 -1.143150 -0.542440 1 -0.548708  0.208520  0.212690 2  1.268021 -0.807303 -3.303072 >>> df.round(3)        A      B      C 0 -0.939 -1.143 -0.542 1 -0.549  0.209  0.213 2  1.268 -0.807 -3.303 The DataFrame.round() method can also accept a dictionary or a Series, to specify a different precision for each column. For instance, the following examples show how to round the first column of df to one decimal place, the second to two, and the third to three decimal places: >>> # Specify column-by-column precision with a dictionary >>> df.round({"A": 1, "B": 2, "C": 3})      A     B      C 0 -0.9 -1.14 -0.542 1 -0.5  0.21  0.213 2  1.3 -0.81 -3.303 >>> # Specify column-by-column precision with a Series >>> decimals = pd.Series([1, 2, 3], index=["A", "B", "C"]) >>> df.round(decimals)      A     B      C 0 -0.9 -1.14 -0.542 1 -0.5  0.21  0.213 2  1.3 -0.81 -3.303 If you need more rounding flexibility, you can apply NumPy's floor(), ceil(), and print() functions to Pandas Series and DataFrame objects: >>> np.floor(df)      A    B    C 0 -1.0 -2.0 -1.0 1 -1.0  0.0  0.0 2  1.0 -1.0 -4.0 >>> np.ceil(df)      A    B    C 0 -0.0 -1.0 -0.0 1 -0.0  1.0  1.0 2  2.0 -0.0 -3.0 >>> np.rint(df)      A    B    C 0 -1.0 -1.0 -1.0 1 -1.0  0.0  0.0 2  1.0 -1.0 -3.0 The modified round_half_up() function from the previous section will also work here: >>> round_half_up(df, decimals=2)       A     B     C 0 -0.94 -1.14 -0.54 1 -0.55  0.21  0.21 2 1.27 -0.81 -3.30Best Practices and ApplicationsNow that you have come across most of the rounding techniques, let us learn some of the best practices to make sure we round numbers in the correct way.Generate More Data and Round LaterSuppose you are dealing with a large set of data, storage can be a problem at times. For example, in an industrial oven you would want to measure the temperature every ten seconds accurate to eight decimal places, using a temperature sensor. These readings will help to avoid large fluctuations which may lead to failure of any heating element or components. We can write a Python script to compare the readings and check for large fluctuations.There will be a large number of readings as they are being recorded each and everyday. You may consider to maintain three decimal places of precision. But again, removing too much precision may result in a change in the calculation. However, if you have enough space, you can easily store the entire data at full precision. With less storage, it is always better to store at least two or three decimal places of precision which are required for calculation.In the end, once you are done computing the daily average of the temperature, you may calculate it to the maximum precision available and finally round the result.Currency Exchange and RegulationsWhenever we purchase an item from a particular place, the tax amount paid against the amount of the item depends largely on geographical factors. An item which costs you $2 may cost you less (say $1.8)  if you buy the same item from a different state. It is due to regulations set forth by the local government.In another case, when the minimum unit of currency at the accounting level in a country is smaller than the lowest unit of physical currency,  Swedish rounding is done. You can find a list of such rounding methods used by various countries if you look up on the  internet.If you want to design any such software for calculating currencies, keep in mind to check the local laws and regulations applicable in your present location.Reduce errorAs you are rounding numbers in a large datasets used in complex computations, your primary concern should be to limit the growth of the error due to rounding.SummaryIn this article we have seen a few methods to round numbers, out of those “rounding half to even” strategy minimizes rounding bias the best. We are lucky to have Python, NumPy, and Pandas already have built-in rounding functions to use this strategy. Here, we have learned about -Several rounding strategies, and how to implement in pure Python.Every rounding strategy inherently introduces a rounding bias, and the “rounding half to even” strategy mitigates this bias well, most of the time.You can round NumPy arrays and Pandas Series and DataFrame objects.If you enjoyed reading this article and found it to be interesting, leave a comment. To learn more about rounding numbers and other features of Python, join our  Python certification course.
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How to Round Numbers in Python

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Swift Vs Python

Programming Languages: Their popularity Every passing year witnesses changes in the preferences of programming languages. Some of them get knocked off the perch, while others continue growing. In recent years, two programming languages stand out from the rest and are rapidly growing in popularity. Those two are Swift and Python. In this article, we will talk about the attributes of Swift and Python, their pros and cons and how they are similar to each other. Read along to know more. What they are  Swift and Python. One is a general-purpose, multi-paradigm, object-oriented, functional, imperative and block-structured language while the latter is a widely-used general-purpose, high-level programming language.  Python was originally designed by Guido van Rossum in 1991 and further developed by Python Software Foundation. It was developed to stress code readability along with its syntax enables programmers to code less to express their concepts. It helps coders to speed up the workflow and integrate systems more efficiently. In a survey by Stack Overflow in 2017, Python was the fastest-growing programming language. This resulted in numerous companies prominently using Python as their programming language, the list including Quora, Netflix, Dropbox, Reddit, Facebook, Spotify, Instagram, etc.  In terms of Python’s usability shown above, Data analysis goes first, followed by web development, machine learning, and DevOps. However, Python is less used for educational purposes, prototyping, and Quality Assurance Services. Now talking about Swift, it was designed and released in 2014 after conducting fresh research on programming languages and by using a modern approach to safety, software design patterns by Apple Inc. It is a completely new programming language for the iOS application, macOS application, watchOS application, tvOS application. Needless to say, it quickly grew to be one of the top 5 programming languages and became the most used programming language among the Apple developer community within a short span of than 5 years, also effectively replacing the previously used Objective C. Let us share an important piece of information with you. According to a survey done on the most popular programming languages, Python takes the first spot with overwhelming popularity with a share of 25.36%, whereas Swift is climbing up the ladder at the 9th spot with 2.69% share. The table is mentioned below:Advantages and disadvantages of using Python  Advantages In this section, we will focus on the criteria that make Python a truly developer-friendly language. As we learnt that Python has its uses in numerous lines of work, we will find out how it ticks the checkboxes of the required criteria. Simplicity and readability One of the prime benefits of using Python is that it is simple to code and read. Of course, it is not a repetitive language to follow but is very similar to English and hence is easy to follow. Moreover, Python is a good choice for beginners in programming Multi-paradigm It is a programming language that is object-oriented as well as procedural. Its procedural paradigm allows reuse code and object-oriented methodology allows varied inheritances and summarising data and functions as one Open-source As Python is open source, you can download and modify its source code. This versatile feature led to the formation of a strong community that keeps growing stronger Integration with other languages Being an extensible and embeddable language, programmers can easily integrate Python to Java applications, C, and C++ Portability and compatibility Python is compatible with various platforms. If required, users do not require to change the code before moving the project. to be moved to another platform Vast collection of libraries Being in the game for a long time, Python boasts having a strong community with a vast range of libraries and frameworks for different purposes. providing programmers with a wide spectrum of opportunities. Additionally, libraries like Pandas, Plotly, NumPy, Pipenv, and others and are included as well. Django, Flask, CherryPy, and PyTorch are.among the most famous frameworks. Disadvantages With the pros come the cons. There is also the other side of a coin that needs attention. In spite of having a long history in the programming world, Python still has several weak sides. Not ideal for Mobile development Python is not a good solution for mobile developers. However, a come-around solution with a few challenges is Kivy - a cross-platform Python framework for developing mobile apps Design restrictions There are specific design limitations in Python. Being dynamically typed language using duck typing, Python automatically identifies a type of a variable and can cause runtime errors Although it is not frequent, it does make errors at times.  Memory consumption Python consumes high memory and is definitely not a good option to run intensive memory tasks. Swift pros and cons Being a relatively new programming language, Swift was launched at the WWDC conference in 2014. According to Apple, the primary features of Swift is that it is fast, modern and interactive. Swift's creator Chris Lattner his creation was a result of ideas inspired by different languages such as C#, Ruby, and especially by Python. That's why we can easily find a couple of similarities between Swift and Python. Nevertheless, let’s see what the pros and cons of Swift are. Advantages Easy to read and maintain The Swift program codes are based on English as it acquired syntaxes from other programming languages, thus making the language more expressive Scalable More features to Swift, so it is a scalable programming language. Swift has already replaced Objective C and Swift is what Apple is relying on Concise Swift does not include long lines of code and that favours the developers who want a concise syntax, thus increasing the development and testing rate of the program Safety and improved performance Almost 40% better than the Objective-C, Swift is handier to tackle the bugs that lead to safer programming when speed and performance is concerned Cross-device support This language can handle a wide range of Apple platforms such as iOS, iOS X, macOS, tvOS, and watchOS Automatic Memory Management This feature prevents memory leaks and helps in optimising the application’s performance that is done by using Automatic Reference Counting. Disadvantages Compatibility issues The updated versions Swift is observed to be a bit unstable with the newer versions of Apple leading to a few issues. Switching to a newer version of Swift is the fix but that is costly Speed Issues This is relevant to the earlier versions of the Swift programming language Less in number: The number of Swift developers is limited as Swift is a new programming language Delay in uploading apps Developers will be facing delays over their apps written in Swift to be uploaded to the App Store only after iOS 8 and Xcode 6 are released. The estimated time for release is reported to be September-October, 2014. Common attributes of Swift and Python Swift and Python are predominantly contrasting languages. Despite that, the do possess some common traits. Let’s see what they are. Both Swift and Python have a distinct syntax and are very similar to the English language. Missing semicolons while coding in either Swift or Python will not result in errors. Both languages have a REPL environment that aids in detecting errors in code and debugging Both are multi-paradigm programming languages They have additional tools to facilitate learning. What makes Swift and Python different from each other? From the previous discussions in this article, it is crystal clear that Swift and Python are fundamentally different from each other. Apple’s Swift is ideal for developing software for the Apple ecosystem while Python can be utilised for use cases but is mainly applied in back-end development. Moreover, as Apple claims, Swift is 8.4x faster than Python in terms of performance. Choosing between Swift and Python depends on the intent of the programmer. If the purpose is developing mobile applications that need to work flawlessly in the Apple platforms, then Swift is the ultimate choice. However, if the intentions are to develop artificial intelligence, design a prototype or build the backend, then Python is the one. In the end, what matters is the intent So now we see that in fact choosing Python or Swift for coding mostly depends on your purpose. If you are fond of developing mobile applications that will work seamlessly on Apple operating systems, you should definitely choose Swift. Python is good in case you want to develop your own artificial intelligence, build the backend or create a prototype. There is no hiding the fact that both Swift and Python are good at what they do. While Python has been a game-changer for years, Swift has been rapidly rising up the ranks. Comparing the two directly is a bit unjust as each one of the two has their own uses. The best person to select the right programming language is you! So be the judge of your decision. Good luck! 
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Swift Vs Python

Programming Languages: Their popularity Every pas... Read More

Top 10 Python IDEs and Code Editors

Over the years, Python language has evolved enormously with the contribution of developers. Python is one of the most popular programming languages. It was designed primarily for server-side web development, software development, evaluation, scripting and artificial intelligence. For this feature Python encloses certain code editors and IDEs that are used for software development say, Python itself. If you are new to programming, learning Python is highly recommended as it is fast, efficient and easy to learn. Python interpreters are available on various operating systems such as Windows, Linux, Mac OS. This article provides a look into code editors and IDEs along with their features, pros and cons and talks about which are the best suited for writing Python codes. But first let us see what are code editors and IDEs. What is a Code Editor? A code editor is built for editing and modifying source code. A standalone text editor is used for writing and editing computer programs. Excellent ones can execute code as well as control a debugger as well as interact with source control systems. Compared to an IDE, a good dedicated code editor is usually smaller and quicker, but is less functional. Typically they are optimized for programming languages. One major feature of a text editor is that they are designed to modify various files and work with whatever language or framework you choose. What is IDE? IDE (Integrated Development Environment) understands the code significantly better than a text editor. It is a program exclusively built for software development. It is designed with a set of tools that all work together:  Text editor  Compiler Build automation Debugging Libraries, and many more to speed up the work.  These tools integrate: An editor designed to frame codes with text formatting, auto-completionetc., build, execution, debugging tools, file management and source and version control. It reduces manual efforts and combines all the equipment in a typical framework. IDE comes with heavy files. Hence, the downloads and installation is quite tedious. IDE requires expertise along with a lot of patience.  How does an IDE and Code editor differ from each other? An IDE is distinctive from code editors in the following ways: Integrated build process:The user does not have to write his own scripts to build apps in an IDE.  File management: IDE has an integrated file management system and deployment tool. It provides support to other framework as well. On the other hand, a Text editor is a simple editor where source code can be edited and it has no other formatting or compiling options. Development Environment: An IDE is mainly used for development purposes as it provides comparatively better features than a text editor. It allows you to write, compile and debug the entire script.  Syntax Highlighting:The editor displays the text message and puts the source code in different colours to improve its readability. Even error messages are displayed in different colours so that the user understands where he has written the wrong code.  Auto completion:It identifies and inserts a common code for the user instantly. This feature acts as an assistance for the programmer. The code suggestion automatically gets displayed.  Debugger: This tool helps the programmer to test and debug the source code of the main program.  Although IDEs have far better features than a Text editor one major significance of Text editor is that it allows modifying all types of files rather than specifying any definite language or types. Features For a good software development, we need code editors and IDEs which help the developer to automate the process of editing, compiling, testing, debugging and much more. Some of the features of these editors are listed below: Good user interface: They allow users to interact and run programs easily. Incredibly fast: Although these IDEs need to import heavy libraries, compile and debug, they offer fast compilation and run time.  Syntax stylizing: Codes are colorized automatically and syntax is highlighted.    Debugging tool: Itruns the code, set breakpoints, examine the variables. Provides good language syntax: IDEs usually work on a specific language but the others are designed for multi-language support. Code editors are designed with multi-language support.  Good source and version control environment: IDEs come with source control feature to keep a track of changes made in source code and other text files during the development of any software. Intelligent code completion:This feature speeds up the coding process by automatically suggesting for incomplete codes. It reduces typos and other common mistakes. Why do we need a good coding environment? For a good software development one seeks a better coding environment. Although features vary from app to app, a definite set of features is required for one. There are many other things involved such as source code control, extension tools, language support etc. Listed below are the core features which make a good coding environment : Retrieve files: All the codes written in an IDE get saved. Also, the programmer can retrieve his code file at the same state where the work is left off. Run within the environment: It should be able to compile and run within the environment where the codes are written. No external file shall be needed to be downloaded for the execution of the programs.  Good Debugging Tool: An IDE or editor should be able to diagnose and  troubleshoot the programmer’s works and highlight the lines with errors if any. A pop-up window should display the error message. This way the programmer can keep a track of his errands and diagnose them.   Automatic formatting tool: Indentation is done automatically as soon as the programmer moves onto the next line. It keeps the code clean and readable. Quick highlighting: keywords, variables and symbols are highlighted. This feature keeps the code clean and easy to understand. Also, pops up the variables making them easy to spot. This makes it a whole lot easier to pick out portions of code than simply looking at a wall of undifferentiated text. Some of the IDEs and code editors There are various Python IDEs and text editors. Some of the IDEs and text editors along with their features and pros and cons are mentioned below: IDLEKey Features: It is an open source IDE entirely written in Python. It is mainly supported by WINDOWS, LINUX, MAC OS etc.. IDLE is a decent IDE for learning because it is lightweight and quite simple to use. IDLE is installed by default as soon as installation of Python is complete. This makes it easier to get started in Python. IDLE features include the Python shell window(interactive interpreter), auto-completion, syntax highlighting, smart indentation, and a basic integrated debugger. It is however not suitable for the completion of larger projects and best suitable for educational purposes only.  Pros A cross-platform where a developer can search within any window, search through multiple files and replace within the windows editor  Supports syntax highlighting, auto code completion, smart indentation and editable configurations Includes Python shell with highlighter Powerful Integrated Debugger with continuous breakpoints, global view, and local spaces Improves the performance  Call stack visibility Increases the flexibility for developers Cons Used for programming just for beginners Limited to handle normal usage issues. Supports basic design  Large software development cannot be handled  Sublime text Key Features: It is a source code editor, supported on all platforms. It is a very popular cross-platform  and a better text editor. It possesses a built-in support for Python for code editing and packages to extend the syntax and editing features. All Sublime Text packages are written in Python and also a Python API. Installation of the packages often requires you to execute scripts directly in Sublime Text. it is designed to support huge programming and markup languages. Additional functions can be applied by the user with the help of plugins.  Pros More reliable for developers and is cross-platform Supports GOTO anything to access files  Generates wide index of each method, class, and function. AllowsUser interface toolkit Easy navigation to words or symbols Multiple selections to change things at one time Offers command palette to sort, edit and modify the syntax and maintain the indentation.  Offers powerful API and package ecosystem Great performance Highly customizable Allows split editing and instant project switch  Better compatibility with language grammar Custom selection on specific projects Cons Not free Installation of extensions is quite tricky Does not support for direct executing or debugging code from within the editor Less active GIT plugin AtomKey Features: It is an open source code editor developed by Github. It is supported on all platforms. It has features similar to that of Python. It has a framework based on atom shells which help to achieve cross platform functionality. With a sleek interface, file system browser, and marketplace for extensions, it offers a framework for creating desktop applications using JavaScript, HTML, CSS . Extensions can be installed when Atom is running.It enables support for third party packages. Its major feature is that although it is a code editor,it can also be used as an IDE. It is also used for educational purposes. Atom is being improvised day by day, striving to make the user experience rewarding and not remain confined to beginners use only.  Pros Cross-platform  Smooth editing Improves performance of its users Offers built-in package manager and file system browser Faster scripting  Offers smart auto-completion  Smart and flexible Supports multiple pane features Easy navigation across an application Simple to use Allows user interface customization Full support from GitHub Quick access to data and information Cons For beginners only Tedious for sorting configurations and plugins Clumsy tabs reduce performance  Slow loading Runs on JavaScript process  Built on Electron, does not run as a native application VimKey Features: Categorized as a stable open source code editor, VI and VIM are modal editors. As it is supported on almost every platform such as: Windows, LINUX, MAC OS, IOS, Android, UNIX, AmigaOS, MorphOS etc. it is highly configurable. Because of its modal mode of operation, it differs from most other text editors. It possesses three basic modes: insert mode, normal or command mode and command line mode. It is easily customized by the addition of extensions and configuration which makes it easily adaptable for Python development.  Pros Free and easily accessible Customizable and persistent  Has a multi-level undo tree  Extensions are added manually Configuration file is modified Multi-buffers support simultaneous file editing Automated indentation  Good user interface Recognition and conversion of file formats Exclusive libraries including wide range of languages Comes with own scripting language with powerful integration, search and replace functionality Extensive system of plugins Allows debugging and refactoring  Provides two different modes to work: normal and editing mode Strings in VIM can be saved and reused  Cons Used as a text editor only No different color for the pop-up option Not good for beginners PyDev Key Features: It is also categorized as an open source IDE mainly written with JAVA.Since it is an eclipse plugin, the Java IDE is transformed into Python IDE. Its integration with Django gives a Python framework. It also has keyword auto-completion, good debugging tool, syntax highlighting and indentation. Pros Free open source Robust IDE feature set Auto-completion of codes and analysis Smart indentation Interactive console shortcuts Integrated with Django configuration  Platform independent Cons: User interface is not great  Visual studioKey Features: It is categorized as an IDE, is a full-featured IDE developed by Microsoft. It is compatible with Windows and Mac OS only and comes with free as well as paid versions. It has its own marketplace for extensions. PTVS(Python Tools for Visual Studio) offers various features as in coding for Python development, IntelliSense, debugging, refactoring etc. Pros Easy and less tedious installation for development purposes Cons Spacious files  Not supported on Linux Visual studio code Key Features: VS code is a code editor and is way more different from VS. It is a free open source code editor developed by Microsoft can be run on platforms such as Windows, Linux and Mac OS X.  It has a full-featured editor that is highly configurable with Python compatibility for software development. Python tools can be added to enable coding in Python.VS code is integrated with Git which promotes it to perform operations like push, commit directly from the editor itself. It also has electron framework for Node JS applications running on the Blink browser engine. It is enclosed with smart code completion with function definition, imported modules and variable types. Apart from these, VS code also comes with syntax highlighting, a debugging console and proprietary IntelliSense code auto completion. After installing Python, VS code recognizes Python files and libraries immediately.  Pros Free and available on every platform  Small, light-weight but highly extensible Huge compatibility Has a powerful code management system Enables debugging from the editor Multi-language support  Extensive libraries Smart user interface and an acceptable layout Cons Slow search engine Tedious launch time Not a native app just like Atom WingKey Features: Wing is also one of the powerful IDEs today and comes with a lot of good features. It is an open source IDE used commercially. It also is constituted with a strong framework and has a strong debugger and smart editor for Python development making it fast, accurate and fun to perform. It comes with a 30 day trial version. It supports text driven development with unit test, PyTest and Django testing framework.  Pros Open source Find and go-to definition Customizable and extensible Auto-code completion Quick Troubleshoot  Source browser shows all the variables used in the script Powerful debugger  Good refactoring  Cons Not capable of supporting dark themes Wing interface is quite intimidating Commercial version is expensive Python-specific IDEs and Editors Anaconda - Jupyter NotebooksKey Features: It is also an open source IDE with a server-client structure, used to create and edit the codes of a Python. Once it is saved, you can share live code equations, visualizations and text. It has anaconda distribution i.e., libraries are preinstalled so downloading the anaconda itself does the task. It supports Python and R language which are installed by default at installation.  This IDE is again used for data science learning. Quite easy to use, it is not just used as an editor but also as an educational tool or presentation. It supports numerical simulation, machine  learning visualization and statistical modelling. Pros Free Open source  Good user interface Server-client structure Educational tool- Data science, Machine learning  Supports numerical simulation  Enables to create, write, edit and insert images Combines code, text and images Integrated libraries - Matplotlib, NumPy, Pandas Multi-language support Auto code completion Cons Sometimes slow loading is experienced Google Colaboratory Key Features: It is the simplest web IDE used for Python. It gives a free GPU access. Instead of downloading heavy files and tedious launch time, one can directly update the files from Colab to the drive. All you need to do is log in to your google account and open Colab. There is no need for extra setup. Unlike other IDEs no files are required to download. Google provides free computation resources with Colaboratory. It is designed for creating machine learning models. For compilation and execution, all you need to do is to update Python package and get started.   Pros Available to all Code can be run without any interruption Highly user interactive No heavy file downloads Integrated libraries Multi-language support Updated in google drive Update the Python package for execution  Runs on cloud Comments can be added in cells Can import Jupiter or IPython notebooks Cons  All colaboratory files are to be stored in google drive Install all specific libraries No access to unsaved files once the session is over Pycharm Key Features: Developed by Jet Brains and one of the widely used full-featured Python IDE, this is a cross-platform IDE for Python programming and  is well-integrated with Python console and IPython Notebook. It is supported by Windows, Linux, Mac OS and other platforms as well. It has massive productivity and saves ample amount of time. It comes with smart code navigation, code editor, good debugging tool, quick refactoring etc. and supports Python web development frameworks such as Angular JS, JavaScript, CSS, HTML  and live editing functions. The paid version offers advanced features such as full database management and a multitude Framework than the community version such as Django, Flask, Google App, Engine, Pyramid and web2py. Pros Great supportive community Brilliant performance. Amazing editing tools Robust debugging tool Smart code navigation Quick and safe refactoring  Built in developer tools Error detection and fix up suggestions Customizable interface Available in free and paid version Cons Slow loading  Installation is quite difficult and may hang up in between SpyderKey Features: It is an open source IDE supported on all platforms. Ranked as one of the best Python compilers, it supports syntax highlighting, auto completion of codes just like Pycharm. It offers an advanced level of editing, debugging, quick diagnose, troubleshoot and many data exploration features. To get started with Spyder, one needs to install anaconda distribution which is basically used in data science and machine learning. Just like Pycharm it has IntelliSense auto-completion of code. Spyder is built on a structured and powerful framework which makes it one of the best IDE used so far. It is most commonly used for scientific development. Pros Free open source IDE Quick troubleshoot Active framework Smart editing and debugging Syntax is automatically highlighted Auto completion of codes Good for data science and machine learning Structured framework Integrates common Python data science libraries like SciPy, NumPy, and Matplotlib Finds and eliminates bottlenecks Explores and edits variables directly from GUI  Performs well in multi-language editor and auto completion mode Cons Spyder is not capable to configure a specific warning Too many plugins degrades its performance ThonnyKey Features: Thonny is another IDE best suited for beginners for Python development and provides a good virtual environment. It is supported on all platforms. It gives a simple debugger with F5, F6 and F7 keys for debugging. Also, Thonny supports highlighting errors, good representation of function calls, auto code completion and smart indentation. It even allows the developers to configure their code and shell commands. by default,  in Thonny Python is pre-installed as it downloads with its own version of Python.  Pros Simple Graphical user interface.  Free open source IDE Best for beginners Simple debugger with F5, F6, F7 Keys Tackles issues with Python interpreters Highlights syntax error Auto-completion of code Good representation of function calls User can change reference mode easily Step through expression evaluation Reply and resolve to comments Cons Interface is not that good for developers Confined to text editing No template support Slow plugin creation Too basic IDE for software development Which Python IDE is right for you? Requirements vary from programmer to programmer. It is one’s own choice to pick the right tool that is best suited for the task at hand. Beginners need to use a simple tool with few customizations whereas experts require tools with advanced features to bring new updates. Few suggestions are listed below:- Beginners should start with IDLE and Thonny as they do not have complex features and are pretty easy to learn. For data science learners Jupyter Notebooks and Google Colaboratory is preferred. Generally, large scale enterprises prefer the paid versions of IDEs like PyCharm, Atom, Sublime Text etc. in order to get extensive service support from the company. Also, they provide easy finance options and manpower. On the other hand, middle and small scale enterprises tend to look for open source tools which provides them with excellent features. Some of such IDEs are Spyder, Pydev, IDLE and Visual Studio. Conclusion Today, Python stands out as one of the most popular programming languages worldwide. IDE being a program dedicated to software development has made it easier for developers to build, execute, and debug their codes. Code editors can only be used for editing codes whereas an IDE is a feature rich editor which has inbuilt text editor, compiler, debugging tool and libraries. Different IDEs and code editors are detailed in this article along with their merits and demerits. Some are suitable for beginners because of their lightweight nature and simplicity like IDLE, Thonny whereas experts require advance featured ones for building software.  For learning purposes say data science, machine learning Jupyter and Google Colaboratory are strongly recommended. Again there are large scale enterprises who prefer PyCharm, Atom, Sublime Text for software development. On the other hand, small scale enterprises prefer Spyder, Pydev, IDLE and Visual Studio. Hence,the type of IDE or code editor that should be used completely depends upon the requirement of the programmer . To gain more knowledge about Python tips and tricks, check our Python tutorial and get a good hold over coding in Python by joining the Python certification course. 
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Top 10 Python IDEs and Code Editors

Over the years, Python language has evolved enormo... Read More