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What are List Methods in Python

Sequence is one of the most basic data types in Python. Every element of a sequence is allocated a unique number called its position or index. The first designated index is zero, the second index is one, and so forth. Although Python comes with six types of pre-installed sequences, the most used ones are lists and tuples, and in this article we would be discussing about lists and its methods.Certain tasks can be performed with all types of sequence; these include adding, multiplying, indexing, slicing, and so on. For added convenience, Python provides built-in functions to find the length of a sequence and to find the largest and smallest elements of the sequence. If you are interested to learn more about other functions and features of Python, you may go through our Python tutorial.What is a ListList is the most versatile data-type available in Python that can be written as a collection of comma-separated values or items between square brackets. The items in a list need not necessarily be homogeneous, i.e. of the same type. This property of List makes it one of the most powerful tools in Python eg:[‘HELLO’, 57, “SKY”]. A single list can contain different Data-Types such as integers, strings, as well as Objects. Lists are mutable, and hence can be changed even after their creation.In Python, lists are ordered in a definite manner and have a definite count. Elements of a list are indexed according to a particular sequence and the indexing is done with 0 being the starting index. Even element of a list has its unique place in the list, which allows duplication of the elements in the list, with each element having its own distinct place and credibility. Lists are a useful tool for storing a sequence of data.Creating a list is as simple as putting different types of comma-separated values between square brackets:list1 = ['jack', 'jill', 1998, 2019];[Text Wrapping Break] list2 = [1, 2, 3, 4, 5 ];[Text Wrapping Break] list3 = ["w", "x", "y", "z"]Just like string indices, list indices start with 0, and lists can be sliced, concatenated and so on.Creating a ListPython Lists can be created just by placing the integer, string, or character inside the square brackets[]. Unlike Sets, a list does not require a built-in function for its creation.# Python program to demonstrate the creation of a list [Text Wrapping Break] # Creating a List [Text Wrapping Break] List = [] [Text Wrapping Break] print("Initial blank List: ") [Text Wrapping Break] print(List) [Text Wrapping Break] [Text Wrapping Break] # Creating a List with  [Text Wrapping Break] # the use of a String [Text Wrapping Break] List = ['PythonListDemo'] [Text Wrapping Break] print("\nList with the use of String: ") [Text Wrapping Break] print(List) [Text Wrapping Break][Text Wrapping Break] # Creating a List with [Text Wrapping Break] # the use of multiple values  [Text Wrapping Break] List = ["Python", "List", "Demo"] [Text Wrapping Break] print("\nList containing multiple values: ") [Text Wrapping Break] print(List[0]) [Text Wrapping Break] print(List[2]) [Text Wrapping Break] [Text Wrapping Break] # Creating a Multi-Dimensional List [Text Wrapping Break] # (By Nesting a list inside a List) [Text Wrapping Break] List = [['Python', 'List'] , ['Demo']] [Text Wrapping Break] print("\nMulti-Dimensional List: ") [Text Wrapping Break] print(List)Initial blank List: [Text Wrapping Break] [] [Text Wrapping Break] [Text Wrapping Break] List with the use of String: [Text Wrapping Break] ['PythonListDemo'] [Text Wrapping Break] [Text Wrapping Break] List containing multiple values: [Text Wrapping Break] Python [Text Wrapping Break] Demo[Text Wrapping Break] [Text Wrapping Break] Multi-Dimensional List:  [Text Wrapping Break] [['Python', 'List'], ['Demo']]Creating a list with multiple distinct or duplicate elements:Multiple distinct or duplicate values can be stored as a sequence during creation of list:# Creating a List with [Text Wrapping Break] # the use of  Numbers [Text Wrapping Break] # (Having duplicate values) [Text Wrapping Break] List = [1, 2, 4, 4, 3, 3, 3, 6, 5] [Text Wrapping Break] print("\nList with the use of Numbers: ")  [Text Wrapping Break] print(List) [Text Wrapping Break]  [Text Wrapping Break] # Creating a List with [Text Wrapping Break] # mixed type of values [Text Wrapping Break] #  (Having numbers and strings) [Text Wrapping Break] List = [1, 2, 'Python', 4, 'List', 6, 'Demo'] [Text Wrapping Break] print("\nList with the use of Mixed Values: ") [Text Wrapping Break] print(List)List with the use of Numbers: [Text Wrapping Break][1, 2, 4, 4, 3, 3, 3, 6,  5] [Text Wrapping Break] [Text Wrapping Break] List with the use of Mixed Values: [Text Wrapping Break] [1, 2, 'Python', 4, 'List', 6, 'Demo'] [Text Wrapping Break]Adding Elements to a ListUsing append() methodUsing the built-in append() function elements can be added to the List. At a time only one element can be added to the list by the use of append() method, but for the addition of multiple elements with the method, loops are used. Unlike Sets, a new List can be added to an existing one with the use of the append() method.# Python program to demonstrate addition of elements in a List [Text Wrapping Break] [Text Wrapping Break] # Creating a List [Text Wrapping Break] List = [] [Text Wrapping Break] print("Initial blank List: ") [Text Wrapping Break] print(List) [Text Wrapping Break] [Text Wrapping Break] #  Addition of Elements  [Text Wrapping Break] # in the List [Text Wrapping Break] List.append(1) [Text Wrapping Break] List.append (2) [Text Wrapping Break] List.append(4) [Text Wrapping Break] print("\nList after Addition of Three elements: ") [Text Wrapping Break] print(List) [Text Wrapping Break] [Text Wrapping Break]# Adding elements to the List [Text Wrapping Break] # using Iterator [Text Wrapping Break] for i in range(1, 4): [Text Wrapping Break] List.append(i) [Text Wrapping Break] print("\nList after Addition of elements from 1-3: ") [Text Wrapping Break] print(List) [Text Wrapping Break] [Text Wrapping Break] # Addition of List to a List [Text Wrapping Break] List2 = ['Python', 'List'] [Text Wrapping Break] List.append(List2) [Text Wrapping Break] print ("\nList after Addition of a List: ") [Text Wrapping Break] print(List)Initial blank List: [Text Wrapping Break] [] [Text Wrapping Break]  [Text Wrapping Break] List after Addition of Three elements: [Text Wrapping Break] [1,2,4][Text Wrapping Break][Text Wrapping Break]List after Addition of elements from 1-3: [Text Wrapping Break] [1, 2, 4, 1, 2, 3] [Text Wrapping Break]  [Text Wrapping Break] List after Addition of a List:[Text Wrapping Break] [1, 2,  4, 1, 2, 3, ['Python', 'List']]Using insert() methodAppend() method restricts the addition of elements at the end of the List only. Using the insert() method, elements can be added to the list at your desired position. Unlike append() which requires only one argument, insert() method requires two arguments for defining the position and value of the element to be inserted (position, value).# Python program to demonstrate addition of elements in a List [Text Wrapping Break] [Text Wrapping Break] # Creating a List  [Text Wrapping Break] List = [1,2,3,4] [Text Wrapping Break] print("Initial List: ") [Text Wrapping Break] print(List) [Text Wrapping Break] [Text Wrapping Break] # Addition of Element at  [Text Wrapping Break] # specific Position [Text Wrapping Break] # (using Insert Method) [Text Wrapping Break] List.insert(3, 12) [Text Wrapping Break] List.insert(0, 'Python') [Text Wrapping Break] print("\nList after performing Insert Operation: ") [Text Wrapping Break] print(List)Initial List: [Text Wrapping Break] [1, 2, 3, 4] [Text Wrapping Break] [Text Wrapping Break] List after performing Insert Operation: [Text Wrapping Break] [ 'Python', 1, 2, 3, 12, 4]Using extend() methodApart from append() and insert() methods, there’s another method to add elements by the use of extend() method. This method is used for adding multiple elements to the end of the list at once.# Python program to demonstrate  [Text Wrapping Break] # Addition of elements in a List [Text Wrapping Break] [Text Wrapping Break] # Creating a List  [Text Wrapping Break] List = [1,2,3,4] [Text Wrapping Break] print("Initial List: ") [Text Wrapping Break] print(List) [Text Wrapping Break] [Text Wrapping Break] #  Addition of multiple elements [Text Wrapping Break] # to the List at the end [Text Wrapping Break] # (using Extend Method)  [Text Wrapping Break] List.extend ( [8,  'Python', 'Program']) [Text Wrapping Break] print( "\nList after performing  Extend Operation: " ) [Text Wrapping Break] print(List)Initial List: [Text Wrapping Break] [1, 2, 3, 4] [Text Wrapping Break]  [Text Wrapping Break] List after performing Extend Operation:  [Text Wrapping Break] [1, 2, 3, 4, 8, 'Python', 'Program']Accessing elements from the ListIn order to access the items in a List, the index number is used as reference. The index operator [ ] is used to access the items of a list. The index should be an integer and nested lists are accessed by using nested indexing.# Python program to demonstrate  [Text Wrapping Break] # accessing of element from list [Text Wrapping Break][Text Wrapping Break] # Creating a List with [Text Wrapping Break]# the use of multiple values [Text Wrapping Break] List = ["Access", "List", "Elements"] [Text Wrapping Break]  [Text Wrapping Break]# accessing an element from the  [Text Wrapping Break] # list using index number [Text Wrapping Break] print("Accessing an element from the list") [Text Wrapping Break] print(List[0])  [Text Wrapping Break] print(List[2]) [Text Wrapping Break]  [Text Wrapping Break] # Creating a Multi-Dimensional List [Text Wrapping Break] # (By Nesting a list inside a List) [Text Wrapping Break] List = [['Access', 'List'] , ['Elements']] [Text Wrapping Break]  [Text Wrapping Break] # accessing an element from the [Text Wrapping Break] # Multi-Dimensional List using [Text Wrapping Break] # index number [Text Wrapping Break] print("Accessing an element from a Multi -  Dimensional list") [Text Wrapping Break] print(List[0][1]) [Text Wrapping Break] print(List[1][0])Accessing an element from the list [Text Wrapping Break] Access [Text Wrapping Break] Elements [Text Wrapping Break] [Text Wrapping Break] Accessing an element from a Multi-Dimensional  list [Text Wrapping Break] List [Text Wrapping Break] ElementsNegative indexingIn Python, negative sequence indexing means the representation of positions of the array from the end. Rather than calculating the offset like List[len(List)-3], we can just write it like List[-3]. Here, -1 refers to the last item, -2 refers to the second last item etc. i.e. beginning from the end.List = [1, 2, 'Python', 4, 'Negative', 6, 'Index'] [Text Wrapping Break] [Text Wrapping Break] # Accessing an element using negative indexing [Text Wrapping Break] print("Accessing element using negative indexing") [Text Wrapping Break]  [Text Wrapping Break] # print the last element of list [Text Wrapping Break] print(List[-1]) [Text Wrapping Break] [Text Wrapping Break]# print the third last element of list  [Text Wrapping Break] print(List[-3])Accessing element using negative indexing [Text Wrapping Break] Index [Text Wrapping Break] NegativeRemoving Elements from the ListUsing remove() methodIn Python, using the built-in remove() function, elements can be removed from the List but an Error will arise if the element is not present in the set. Remove() method is only capable of removing one element at a time, to remove a range of elements, an iterator is used. A limitation of this method is that it will only remove the first occurrence of the searched element and would not work if there are multiple occurrences of the searched element.# Python program to demonstrate removal of elements in a List [Text Wrapping Break][Text Wrapping Break] # Creating a List [Text Wrapping Break] List = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12] [Text Wrapping Break] print("Initial List: ") [Text Wrapping Break] print(List) [Text Wrapping Break]  [Text Wrapping Break] # Removing elements from List [Text Wrapping Break] # using Remove() method [Text Wrapping Break] List.remove(5) [Text Wrapping Break] List.remove(6) [Text Wrapping Break] print("\nList after removal of two elements: ") [Text Wrapping Break] print(List) [Text Wrapping Break]  [Text Wrapping Break] # Removing elements from List [Text Wrapping Break] # using iterator method [Text Wrapping Break] for i in range(1, 5): [Text Wrapping Break]    List.remove(i) [Text Wrapping Break] print("\nList after removing a range of elements: ") [Text Wrapping Break] print(List)Initial List: [Text Wrapping Break][1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12] [Text Wrapping Break][Text Wrapping Break]List after removal of two elements: [Text Wrapping Break][1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12][Text Wrapping Break] [Text Wrapping Break] List after removing a range of elements: [Text Wrapping Break] [7, 8, 9, 10, 11, 12]Using pop() methodIn Python,  we can also remove and return an element from the set using the Pop() function, but it removes  the last element of the set only by default. To remove a specific element from a position of the List, index of the element is passed as an argument to the pop() function.List = [1,2,3,4,5] [Text Wrapping Break] [Text Wrapping Break] # Removing element from the  [Text Wrapping Break] # Set using the pop() method [Text Wrapping Break] List.pop() [Text Wrapping Break] print("\nList after popping an element: ") [Text Wrapping Break] print(List) [Text Wrapping Break]  [Text Wrapping Break] # Removing element at a  [Text Wrapping Break] # specific location from the  [Text Wrapping Break] # Set using the pop() method [Text Wrapping Break] List.pop(2) [Text Wrapping Break] print("\nList after popping a specific element: ") [Text Wrapping Break] print(List)List after popping an element: [Text Wrapping Break] [1, 2, 3, 4]  [Text Wrapping Break][Text Wrapping Break]List after popping a specific  element: [Text Wrapping Break][1, 2, 4]Slicing of a ListAlthough there are several ways to print the whole List with all the elements in Python, there is only one way to print a specific range of elements from the list: by the use of Slice operation. Slice operation is performed on Lists by the use of colon(:). For printing elements from the beginning of the range use [:Index], for printing elements from end use [:-Index], to print elements from a specific index till the end use [Index:], for printing elements within a specific range, use [Start Index: End Index] and to print the entire List by the use of slicing operation, use [:]. Moreover, in order to print entire List in reverse order, use [::-1]. For printing the elements of List from rear end, negative indexes are used.# Python program to demonstrate removal of elements in a List [Text Wrapping Break][Text Wrapping Break]# Creating a List [Text Wrapping Break] List = ['P', 'Y', 'T', 'H','O', 'N', 'P', 'R', 'O', 'G', 'R', 'A', 'M'] [Text Wrapping Break] print("Initial List: ") [Text Wrapping Break] print(List) [Text Wrapping Break]  [Text Wrapping Break] # Print elements of a range [Text Wrapping Break] # using Slice operation [Text Wrapping Break] Sliced_List = List[3:10] [Text Wrapping Break] print("\nSlicing elements in a range 3-10: ") [Text Wrapping Break] print(Sliced_List) [Text Wrapping Break]  [Text Wrapping Break] # Print elements from a  [Text Wrapping Break] # pre-defined point to end [Text Wrapping Break] Sliced_List = List[6:] [Text Wrapping Break] print("\nElements sliced from 6th ""element till the end: ") [Text Wrapping Break] print(Sliced_List) [Text Wrapping Break] [Text Wrapping Break]# Printing elements from [Text Wrapping Break] # beginning till end [Text Wrapping Break] Sliced_List = List[:] [Text Wrapping Break] print("\nPrinting all elements using slice operation: ") [Text Wrapping Break] print(Sliced_List) Initial List: [Text Wrapping Break] ['P', 'Y', 'T', 'H','O', 'N', 'P', 'R', 'O', 'G', 'R', 'A', 'M'] [Text Wrapping Break] [Text Wrapping Break] Slicing elements in a range 3-10: [Text Wrapping Break]['H', 'O', 'N', 'P', 'R','O','G'][Text Wrapping Break][Text Wrapping Break]Elements sliced from 6th element till the end: [Text Wrapping Break]['P', 'R', 'O', 'G', 'R', 'A', 'M'][Text Wrapping Break][Text Wrapping Break]Printing all elements using slice operation: [Text Wrapping Break] ['P', 'Y', 'T', 'H', 'O', 'N', 'P', 'R', 'O', 'G', 'R', 'A', 'M']Negative index List Slicing# Creating a List [Text Wrapping Break] List = ['P', 'Y', 'T', 'H','O', 'N', 'P', 'R', 'O', 'G', 'R', 'A', 'M'] [Text Wrapping Break] print("Initial List: ") [Text Wrapping Break] print(List) [Text Wrapping Break]  [Text Wrapping Break] # Print elements from beginning [Text Wrapping Break] # to a pre-defined point using Slice [Text Wrapping Break] Sliced_List = List[:-7] [Text Wrapping Break] print("\nElements sliced till 7th element from last: ") [Text Wrapping Break] print(Sliced_List) [Text Wrapping Break]  [Text Wrapping Break] #  Print elements of a range [Text Wrapping Break] # using negative index List slicing [Text Wrapping Break] Sliced_List = List[-6:-1] [Text Wrapping Break] print("\nElements sliced from index -6 to -1") [Text Wrapping Break] print(Sliced_List) [Text Wrapping Break]  [Text Wrapping Break] #  Printing elements in reverse [Text Wrapping Break] # using Slice operation [Text Wrapping Break] Sliced_List = List[::-1] [Text Wrapping Break] print("\nPrinting List in reverse: ") [Text Wrapping Break] print(Sliced_List)Initial List: [Text Wrapping Break] ['P', 'Y', 'T', 'H','O', 'N', 'P', 'R', 'O', 'G', 'R', 'A', 'M'][Text Wrapping Break] [Text Wrapping Break]Elements sliced till 7th element from last: [Text Wrapping Break]['P', 'Y', 'T', 'H', 'O', 'N'][Text Wrapping Break] [Text Wrapping Break]Elements sliced from index -6 to -1[Text Wrapping Break] ['R', 'O', 'G', 'R', 'A'][Text Wrapping Break] [Text Wrapping Break]Printing List in reverse:[Text Wrapping Break]['M', 'A', 'R', 'G', 'O', 'R', 'P', 'N', 'O', 'H', 'T', 'Y', 'P']Updating ListsYou can update single or multiple elements of lists by reassigning the values on the lists individually.# Python program to update elements of a list[Text Wrapping Break]list = ['physics', 'chemistry', 1998, 2019];[Text Wrapping Break] print "Value available at index 2 : "[Text Wrapping Break] print list[2] [Text Wrapping Break] list[2] = 2000;[Text Wrapping Break] print "New value available at index 2 : "[Text Wrapping Break] print list[2]Value available at index 2 : [Text Wrapping Break] 1998 [Text Wrapping Break] New value available at index 2 : [Text Wrapping Break] 2000Built-in functionsFUNCTION DESCRIPTIONsum() Addsall numbers.ord() Used for returning an integer which represents the unique Unicode code point of the given Unicode character.cmp() If the first list is “greater” than the second list, the function returns 1.max() It returns the largest element in the list.min() It returns the smallest element in the list.all() It returns true if all elements are true or false if any element in the list is empty.any() It returns true if even one of the elements of the list is true. If one list is empty, it returns false.len() It returns length the list.enumerate() It adds a counter to an enumerate object that can be used directly for loops.accumulate() It makes an iterator that gives the result of a function. It takes a function as an argument.filter() It can individually check if every element is true or not.map() It applies a particular function to each item of an iterable and shows a list of the results.lambda() It is an anonymous function that behaves like a normal function in regard to arguments. While normal functions are defined with def keyword, anonymous functions are defined using lambda keyword.List MethodsFUNCTION DESCRIPTIONAppend() Adds an element at the end of the listExtend() Adds all elements of one list to another listInsert() Inserts an item at a desired indexRemove() Removes an item from the listPop() Removes and returns an element at a desired indexClear() Removes all elements from the listIndex() Returns the index of the first identical itemCount() Returns the number of items passed as argumentSort() Sort items of a list in ascending orderReverse() Reverses the listcopy() Returns a copy of the listSummaryIn this article, we have covered the concept of Lists in Python. You have learned the basics of creating a List, adding value to it, accessing its elements, removing the elements, and various other operations. We have also covered some basic built-in functions of Python and several other methods along with their functions. 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.

What are List Methods in Python

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What are List Methods in Python

Sequence is one of the most basic data types in Python. Every element of a sequence is allocated a unique number called its position or index. The first designated index is zero, the second index is one, and so forth. Although Python comes with six types of pre-installed sequences, the most used ones are lists and tuples, and in this article we would be discussing about lists and its methods.

Certain tasks can be performed with all types of sequence; these include adding, multiplying, indexing, slicing, and so on. For added convenience, Python provides built-in functions to find the length of a sequence and to find the largest and smallest elements of the sequence. If you are interested to learn more about other functions and features of Python, you may go through our Python tutorial.

What is a List

List is the most versatile data-type available in Python that can be written as a collection of comma-separated values or items between square brackets. The items in a list need not necessarily be homogeneous, i.e. of the same type. This property of List makes it one of the most powerful tools in Python eg:[‘HELLO’, 57, “SKY”]. A single list can contain different Data-Types such as integers, strings, as well as Objects. Lists are mutable, and hence can be changed even after their creation.

In Python, lists are ordered in a definite manner and have a definite count. Elements of a list are indexed according to a particular sequence and the indexing is done with 0 being the starting index. Even element of a list has its unique place in the list, which allows duplication of the elements in the list, with each element having its own distinct place and credibility. Lists are a useful tool for storing a sequence of data.

Creating a list is as simple as putting different types of comma-separated values between square brackets:

list1 = ['jack', 'jill', 1998, 2019];[Text Wrapping Break] list2 = [1, 2,
 3, 4, 5 ];[Text Wrapping Break] list3 = ["w", "x", "y", "z"]

Just like string indices, list indices start with 0, and lists can be sliced, concatenated and so on.

Creating a List

Python Lists can be created just by placing the integer, string, or character inside the square brackets[]. Unlike Sets, a list does not require a built-in function for its creation.

# Python program to demonstrate the creation of a list
[Text Wrapping Break] # Creating a List [Text Wrapping Break] List = []
[Text Wrapping Break] print("Initial blank List: ")
[Text Wrapping Break] print(List) [Text Wrapping Break] [Text Wrapping Break] #
Creating a List with  [Text Wrapping Break] # the use of a String
[Text Wrapping Break] List = ['PythonListDemo']
[Text Wrapping Break] print("\nList with the use of String: ")
[Text Wrapping Break] print(List) [Text Wrapping Break][Text Wrapping Break] # 
Creating a List with [Text Wrapping Break] # the use of multiple values 
[Text Wrapping Break] List = ["Python""List""Demo"]
[Text Wrapping Break] print("\nList containing multiple values: ")
[Text Wrapping Break] print(List[0]) [Text Wrapping Break] print(List[2])
[Text Wrapping Break] [Text Wrapping Break] # Creating a Multi-Dimensional List
[Text Wrapping Break] # (By Nesting a list inside a List) [Text Wrapping Break] List = [['Python', 'List'] , ['Demo']]
[Text Wrapping Break] print("\nMulti-Dimensional List: ")
[Text Wrapping Break] print(List)
Initial blank List:
[Text Wrapping Break]
[] [Text Wrapping Break] [Text Wrapping Break]
List with the use of String:
[Text Wrapping Break]
['PythonListDemo'] [Text Wrapping Break]
[Text Wrapping Break] List 
containing multiple values:
[Text Wrapping Break] Python [Text Wrapping Break]
Demo[Text Wrapping Break] [Text Wrapping Break]
Multi-Dimensional List: 
[Text Wrapping Break] [['Python',
'List'], ['Demo']]

Creating a list with multiple distinct or duplicate elements:

Multiple distinct or duplicate values can be stored as a sequence during creation of list:

# Creating a List with [Text Wrapping Break] # the use of 
Numbers [Text Wrapping Break] # (Having duplicate values)
[Text Wrapping Break] List = [1, 2, 4, 4, 3, 3, 3, 6, 5]
[Text Wrapping Break] print("\nList with the use of Numbers: "[Text Wrapping Break] print(List) [Text Wrapping Break] 
[Text Wrapping Break] # Creating a List with
[Text Wrapping Break] # mixed type of values [Text Wrapping Break] # 
(Having numbers and strings) [Text Wrapping Break] List = [1,
2, 'Python', 4, 'List', 6, 'Demo']
[Text Wrapping Break] print("\nList with the use of Mixed
Values: ") [Text Wrapping Break] print(List)
List with the use of Numbers: [Text Wrapping Break][1, 2, 4, 4, 3, 3, 3, 6, 
5] [Text Wrapping Break] [Text Wrapping Break] List with the use of Mixed Values:
[Text Wrapping Break] [1, 2, 'Python', 4, 'List', 6, 'Demo'] [Text Wrapping Break]

Adding Elements to a List

Using append() method

Using the built-in append() function elements can be added to the List. At a time only one element can be added to the list by the use of append() method, but for the addition of multiple elements with the method, loops are used. Unlike Sets, a new List can be added to an existing one with the use of the append() method.

# Python program to demonstrate addition of elements in a List
[Text Wrapping Break] [Text Wrapping Break] # Creating a List
[Text Wrapping Break] List = [] [Text Wrapping Break] print("Initial blank List: ")
[Text Wrapping Break] print(List) [Text Wrapping Break] [Text Wrapping Break] # 
Addition of Elements  [Text Wrapping Break] # in the List
[Text Wrapping Break] List.append(1) [Text Wrapping Break] List.append (2)
[Text Wrapping Break] List.append(4) [Text Wrapping Break] print("\nList after
Addition of Three elements: ") [Text Wrapping Break] print(List)
[Text Wrapping Break] [Text Wrapping Break]# Adding elements to the List
[Text Wrapping Break] # using Iterator [Text Wrapping Break] for i in range(1, 4):
[Text Wrapping Break] List.append(i) [Text Wrapping Break] print("\nList after
Addition of elements from 1-3: ") [Text Wrapping Break] print(List)
[Text Wrapping Break] [Text Wrapping Break] # Addition of List to a List
[Text Wrapping Break] List2 = ['Python', 'List']
[Text Wrapping Break] List.append(List2) [Text Wrapping Break] print ("\nList after
Addition of a List: ") [Text Wrapping Break] print(List)
Initial blank List: [Text Wrapping Break] [] [Text Wrapping Break] 
[Text Wrapping Break] List after Addition of Three elements: [Text Wrapping Break]
[1,2,4][Text Wrapping Break][Text Wrapping Break]List after Addition of
elements from 1-3[Text Wrapping Break] [1, 2, 4, 1, 2, 3[Text Wrapping Break] 
[Text Wrapping Break] List after Addition of a List:[Text Wrapping Break] [1, 2, 
4, 1, 2, 3, ['Python', 'List']]

Using insert() method

Append() method restricts the addition of elements at the end of the List only. Using the insert() method, elements can be added to the list at your desired position. Unlike append() which requires only one argument, insert() method requires two arguments for defining the position and value of the element to be inserted (position, value).

# Python program to demonstrate addition of elements in a List
[Text Wrapping Break] [Text Wrapping Break] # Creating a List 
[Text Wrapping Break] List = [1,2,3,4] [Text Wrapping Break] print("Initial List: 
") [Text Wrapping Break] print(List) [Text Wrapping Break] [Text Wrapping Break] #
Addition of Element at  [Text Wrapping Break] # specific Position
[Text Wrapping Break] # (using Insert Method) [Text Wrapping Break] List.insert(3,
12) [Text Wrapping Break] List.insert(0, 'Python')
[Text Wrapping Break] print("\nList after performing Insert Operation: ")
[Text Wrapping Break] print(List)
Initial List: [Text Wrapping Break] [1, 2, 3, 4] [Text Wrapping Break]
[Text Wrapping Break] List after performing Insert Operation:
[Text Wrapping Break] [ 'Python', 1, 2, 3, 12, 4]

Using extend() method

Apart from append() and insert() methods, there’s another method to add elements by the use of extend() method. This method is used for adding multiple elements to the end of the list at once.

# Python program to demonstrate  [Text Wrapping Break] # Addition of elements
in a List [Text Wrapping Break] [Text Wrapping Break] # Creating a List 
[Text Wrapping Break] List = [1,2,3,4] [Text Wrapping Break] print("Initial List:
") [Text Wrapping Break] print(List) [Text Wrapping Break] [Text Wrapping Break] # 
Addition of multiple elements [Text Wrapping Break] # to the List at the end
[Text Wrapping Break] # (using Extend Method) 
[Text Wrapping Break] List.extend ( [8,
 'Python', 'Program']) [Text Wrapping Break] print( "\nList after performing 
Extend Operation: " ) [Text Wrapping Break] print(List)
Initial List: [Text Wrapping Break] [1, 2, 3, 4] [Text Wrapping Break] 
[Text Wrapping Break] List after performing Extend Operation: 
[Text Wrapping Break] [1, 2, 3, 4, 8, 'Python', 'Program']

Accessing elements from the List

In order to access the items in a List, the index number is used as reference. The index operator [ ] is used to access the items of a list. The index should be an integer and nested lists are accessed by using nested indexing.

# Python program to demonstrate  [Text Wrapping Break] # accessing of element
from list [Text Wrapping Break][Text Wrapping Break] # Creating a List with
[Text Wrapping Break]# the use of multiple values [Text Wrapping Break] List =
["Access", "List", "Elements"] [Text Wrapping Break]  [Text Wrapping Break]#
accessing an element from the  [Text Wrapping Break] # list using index number
[Text Wrapping Break] print("Accessing an element from the list")
[Text Wrapping Break] print(List[0])  [Text Wrapping Break] print(List[2])
[Text Wrapping Break]  [Text Wrapping Break] # Creating a Multi-Dimensional List
[Text Wrapping Break] # (By Nesting a list inside a List)
[Text Wrapping Break] List = [['Access', 'List'] , ['Elements']]
[Text Wrapping Break]  [Text Wrapping Break] # accessing an element from the
[Text Wrapping Break] # Multi-Dimensional List using [Text Wrapping Break] # index
number [Text Wrapping Break] print("Accessing an element from a Multi - 
Dimensional list") [Text Wrapping Break] print(List[0][1])
[Text Wrapping Break] print(List[1][0])
Accessing an element from the
list [Text Wrapping Break] Access [Text Wrapping Break] Elements [Text Wrapping Break] [Text Wrapping Break]
Accessing an element from a Multi-Dimensional
 list [Text Wrapping Break] List [Text Wrapping Break] Elements

Negative indexing

In Python, negative sequence indexing means the representation of positions of the array from the end. Rather than calculating the offset like List[len(List)-3], we can just write it like List[-3]. Here, -1 refers to the last item, -2 refers to the second last item etc. i.e. beginning from the end.

List = [1, 2, 'Python', 4, 'Negative', 6, 'Index'] [Text Wrapping Break]
[Text Wrapping Break] # Accessing an element using negative indexing
[Text Wrapping Break] print("Accessing element using negative indexing")
[Text Wrapping Break]  [Text Wrapping Break] # print the last element of list
[Text Wrapping Break] print(List[-1]) [Text Wrapping Break] [Text Wrapping Break]#
print the third last element of list  [Text Wrapping Break] print(List[-3])
Accessing element using negative
indexing [Text Wrapping Break] Index [Text Wrapping Break] Negative

Removing Elements from the List

Using remove() method

In Python, using the built-in remove() function, elements can be removed from the List but an Error will arise if the element is not present in the set. Remove() method is only capable of removing one element at a time, to remove a range of elements, an iterator is used. A limitation of this method is that it will only remove the first occurrence of the searched element and would not work if there are multiple occurrences of the searched element.

# Python program to demonstrate removal of elements in a List
[Text Wrapping Break][Text Wrapping Break] # Creating a List
[Text Wrapping Break] List = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
[Text Wrapping Break] print("Initial List: ") [Text Wrapping Break] print(List)
[Text Wrapping Break]  [Text Wrapping Break] # Removing elements from List
[Text Wrapping Break] # using Remove() method [Text Wrapping Break] List.remove(5)
[Text Wrapping Break] List.remove(6) [Text Wrapping Break] print("\nList after
removal of two elements: ") [Text Wrapping Break] print(List)
[Text Wrapping Break]  [Text Wrapping Break] # Removing elements from List
[Text Wrapping Break] # using iterator method [Text Wrapping Break] for i in
range(1, 5): [Text Wrapping Break]    List.remove(i)
[Text Wrapping Break] print("\nList after removing a range of elements: ")
[Text Wrapping Break] print(List)
Initial List: [Text Wrapping Break][1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
[Text Wrapping Break][Text Wrapping Break]List after removal of two elements:
[Text Wrapping Break][1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12][Text Wrapping Break]
[Text Wrapping Break] List after removing a range of elements:
[Text Wrapping Break] [7, 8, 9, 10, 11, 12]

Using pop() method

In Python,  we can also remove and return an element from the set using the Pop() function, but it removes  the last element of the set only by default. To remove a specific element from a position of the List, index of the element is passed as an argument to the pop() function.

List = [1,2,3,4,5] [Text Wrapping Break] [Text Wrapping Break] # Removing element
from the  [Text Wrapping Break] # Set using the pop() method
[Text Wrapping Break] List.pop() [Text Wrapping Break] print("\nList after popping
an element: ") [Text Wrapping Break] print(List) [Text Wrapping Break] 
[Text Wrapping Break] # Removing element at a  [Text Wrapping Break] # specific
location from the  [Text Wrapping Break] # Set using the pop() method
[Text Wrapping Break] List.pop(2) [Text Wrapping Break] print("\nList after popping
a specific element: ") [Text Wrapping Break] print(List)
List after popping an element: [Text Wrapping Break] [1, 2, 3, 4[Text Wrapping Break][Text Wrapping Break]List after popping a specific 
element: [Text Wrapping Break][1, 2, 4]

Slicing of a List

Although there are several ways to print the whole List with all the elements in Python, there is only one way to print a specific range of elements from the list: by the use of Slice operation. Slice operation is performed on Lists by the use of colon(:). For printing elements from the beginning of the range use [:Index], for printing elements from end use [:-Index], to print elements from a specific index till the end use [Index:], for printing elements within a specific range, use [Start Index: End Index] and to print the entire List by the use of slicing operation, use [:]. Moreover, in order to print entire List in reverse order, use [::-1]. For printing the elements of List from rear end, negative indexes are used.

# Python program to demonstrate removal of elements in a List
[Text Wrapping Break][Text Wrapping Break]# Creating a List
[Text Wrapping Break] List =
['P', 'Y', 'T', 'H','O', 'N', 'P', 'R', 'O', 'G', 'R', 'A', 'M']
[Text Wrapping Break] print("Initial List: ") [Text Wrapping Break] print(List)
[Text Wrapping Break]  [Text Wrapping Break] # Print elements of a range
[Text Wrapping Break] # using Slice operation [Text Wrapping Break] Sliced_List =
List[3:10] [Text Wrapping Break] print("\nSlicing elements in a range 3-10: ")
[Text Wrapping Break] print(Sliced_List) [Text Wrapping Break]  [Text Wrapping Break] #
Print elements from a  [Text Wrapping Break] # pre-defined point to end
[Text Wrapping Break] Sliced_List = List[6:]
[Text Wrapping Break] print("\nElements sliced from 6th ""element till the
end: ") [Text Wrapping Break] print(Sliced_List) [Text Wrapping Break]
[Text Wrapping Break]# Printing elements from [Text Wrapping Break] # beginning
till end [Text Wrapping Break] Sliced_List = List[:]
[Text Wrapping Break] print("\nPrinting all elements using slice operation: ")
[Text Wrapping Break] print(Sliced_List) 
Initial List: [Text Wrapping Break]
['P', 'Y', 'T', 'H','O', 'N', 'P', 'R', 'O', 'G', 'R', 'A', 'M'[Text Wrapping Break]
[Text Wrapping Break] Slicing elements in a range 3-10: [Text Wrapping Break]['H',
'O', 'N', 'P', 'R','O','G'][Text Wrapping Break][Text Wrapping Break]Elements
sliced from 6th element till the end: [Text Wrapping Break]['P', 'R', 'O',
'G', 'R', 'A', 'M'][Text Wrapping Break][Text Wrapping Break]Printing all
elements using slice operation: [Text Wrapping Break] ['P', 'Y', 'T', 'H',
'O', 'N', 'P', 'R', 'O', 'G', 'R', 'A', 'M']

Negative index List Slicing

# Creating a List [Text Wrapping Break] List =
['P', 'Y', 'T', 'H','O', 'N', 'P', 'R', 'O', 'G', 'R', 'A', 'M']
[Text Wrapping Break] print("Initial List: ") [Text Wrapping Break] print(List)
[Text Wrapping Break]  [Text Wrapping Break] # Print elements from beginning
[Text Wrapping Break] # to a pre-defined point using Slice
[Text Wrapping Break] Sliced_List = List[:-7]
[Text Wrapping Break] print("\nElements sliced till 7th element from last: ")
[Text Wrapping Break] print(Sliced_List) [Text Wrapping Break]  [Text Wrapping Break] #
 Print elements of a range [Text Wrapping Break] # using negative index List
slicing [Text Wrapping Break] Sliced_List = List[-6:-1]
[Text Wrapping Break] print("\nElements sliced from index -6 to -1")
[Text Wrapping Break] print(Sliced_List) [Text Wrapping Break]  [Text Wrapping Break] #
 Printing elements in reverse [Text Wrapping Break] # using Slice operation
[Text Wrapping Break] Sliced_List = List[::-1]
[Text Wrapping Break] print("\nPrinting List in reverse: ")
[Text Wrapping Break] print(Sliced_List)
Initial List: [Text Wrapping Break]
['P', 'Y', 'T', 'H','O', 'N', 'P', 'R', 'O', 'G', 'R', 'A', 'M'][Text Wrapping Break]
[Text Wrapping Break]Elements sliced till 7th element from last:
[Text Wrapping Break]['P', 'Y', 'T', 'H', 'O', 'N'][Text Wrapping Break]
[Text Wrapping Break]Elements sliced from index -6 to -1[Text Wrapping Break]
['R', 'O', 'G', 'R', 'A'][Text Wrapping Break] [Text Wrapping Break]Printing List
in reverse:[Text Wrapping Break]['M', 'A', 'R', 'G', 'O', 'R', 'P', 'N',
'O', 'H', 'T', 'Y', 'P']

Updating Lists

You can update single or multiple elements of lists by reassigning the values on the lists individually.

# Python program to update elements of a list[Text Wrapping Break]list =
['physics', 'chemistry', 1998, 2019];[Text Wrapping Break] print "Value
available at index 2 : "[Text Wrapping Break] print list[2]
[Text Wrapping Break] list[2] = 2000;[Text Wrapping Break] print "New value
available at index 2 : "[Text Wrapping Break] print list[2]
Value available at index 2 : [Text Wrapping Break] 1998 [Text Wrapping Break] New
value available at index 2 : [Text Wrapping Break] 2000

Built-in functions

FUNCTION DESCRIPTION

sum() Addsall numbers.

ord() Used for returning an integer which represents the unique Unicode code point of the given Unicode character.

cmp() If the first list is “greater” than the second list, the function returns 1.

max() It returns the largest element in the list.

min() It returns the smallest element in the list.

all() It returns true if all elements are true or false if any element in the list is empty.

any() It returns true if even one of the elements of the list is true. If one list is empty, it returns false.

len() It returns length the list.

enumerate() It adds a counter to an enumerate object that can be used directly for loops.

accumulate() It makes an iterator that gives the result of a function. It takes a function as an argument.

filter() It can individually check if every element is true or not.

map() It applies a particular function to each item of an iterable and shows a list of the results.

lambda() It is an anonymous function that behaves like a normal function in regard to arguments. While normal functions are defined with def keyword, anonymous functions are defined using lambda keyword.

List Methods

FUNCTION DESCRIPTION

Append() Adds an element at the end of the list

Extend() Adds all elements of one list to another list

Insert() Inserts an item at a desired index

Remove() Removes an item from the list

Pop() Removes and returns an element at a desired index

Clear() Removes all elements from the list

Index() Returns the index of the first identical item

Count() Returns the number of items passed as argument

Sort() Sort items of a list in ascending order

Reverse() Reverses the list

copy() Returns a copy of the list

Summary

In this article, we have covered the concept of Lists in Python. You have learned the basics of creating a List, adding value to it, accessing its elements, removing the elements, and various other operations. We have also covered some basic built-in functions of Python and several other methods along with their functions. 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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You can also add customized data, view options, and passwords to the documents. Tabula-pyIt is a Python wrapper of tabula-java which can read tables from PDF files and convert into Pandas Dataframe or into CSV/TSV/JSON file formats.SlateIt is a Python package which facilitates the extraction of information and is dependent on the PdfMiner package.PDFQueryA light Python wrapper which uses minimum code to extract data from PDFs.xPDFIt is an open source viewer of PDF which also includes an extractor, converter and other utilities. Out of all the libraries mentioned above, PyPDF2 is the most used to perform operations like extraction, merging, splitting and so on.Installing PyPDF2If you're using Anaconda, you can install PyPDF2 using pip or conda. To install PyPDF2 using pip, run the following command in the command line:pip install PyPDF2The module is case-sensitive. So you need to make sure that proper syntax is followed. The installation is really quick since PyPDF2 is free of dependencies.Extracting Document Information from a PDF in PythonPyPDF2 can be used to extract metadata and all sorts of texts from PDF when you are performing operations on preexisting PDF files. The types of data you can extract are:AuthorCreatorProducerSubjectTitleNumber of PagesTo understand it better, let us use an existing PDF in your system or you can go to Leanpub and download a book sample.The code for extracting the document information from the PDF—# get_doc_info.py from PyPDF2 import PdfFileReader def getinfo(path):     with open(path, 'rb') as f:         PDF = PdfFileReader(f)         information = PDF.getDocumentInfo()         numberofpages = PDF.getNumPages()     print(information)     author = information.author     creator = information.creator     producer =information .producer     subject = information.subject     title = information.title if __name__ == '__main__':     path = 'reportlab-sample.pdf'     getinfo(path)The output of the program above will look like—Here, we have firstly imported PdfFileReader from the PyPDF2 package. The class PdfFileReader is used to interact with PDF files like reading and extracting information using accessor methods. Then, we have created our own function getinfo with a PDF file as an argument and then called the getdocumentinfo(). This returned an instance of DocumentInformation. And finally we got extract information like the author, creator, subject or title, etc.getNumPages() is used to count the number of pages in the document. PdfMiner can be used when you want to extract text from a PDF file. It is potent and particularly designed for extracting text from PDF.We have learned to extract information from PDF. Now let’s learn how to rotate a PDF. Rotating pages in PDFA lot of times we receive PDFs which contain pages in landscape orientation instead of portrait. You may also find certain documents to be upside down, which happens while scanning a document or mailing. However, we can rotate the pages clockwise or counterclockwise according to our choice using Python with PyPDF2.The code for rotating the article is as follows—# rotate_pages.py from PyPDF2 import PdfFileReader, PdfFileWriter def rotate(pdf_path):     pdf_write = PdfFileWriter()     pdf_read = PdfFileReader(path)     # Rotate page 90 degrees to the right     page1 = pdf_read.getPage(0).rotateClockwise(90)     pdf_write.addPage(page1)     # Rotate page 90 degrees to the left     page2 = pdf_read.getPage(1).rotateCounterClockwise(90)     pdf_write.addPage(page2)     # Add a page in normal orientation     pdf_write.addPage(pdf_read.getPage(2))     with open('rotate_pages.pdf', 'wb') as fh:         pdf_write.write(fh) if __name__ == '__main__':     path = 'mldocument.pdf'     rotate(path)The output of the code will be as follows—Here firstly we imported the PdfFileReader and the PdfFileWriter so that we can write out a new PDF file. Then we declared a function rotate with a path to the PDF that is to be modified. Within the function, we created a read object pdf_read and write object pdf_write.Then, we used the getPage() to grab the pages. Two pages page1 and page2 are taken and rotated to 90 degrees clockwise and 90 degrees counterclockwise respectively using rotateClockwise() and rotateCounterClockwise().We used addPage() function after each rotation method calls. This adds the rotated page to the write object. The last page we add is page3 without any rotation.Lastly, we have used write() with a file-like parameter to write out the new PDF. The final PDF contains three pages, the first two will be in the landscape mode and rotated in reversed direction and the third page will be in normal orientation.Now we will learn to merge different PDFs into one.Merging PDFsIn many cases, we need to merge two PDFs into a single one. For example, suppose you are working on a project report and you need to print it and bind it into a book. It contains a cover page followed by the project report. So you have two different PDFs and you want to merge them into one PDF. You can simply use Python to do so. Let us see how can we merge PDFs into one.The code for merging two PDF documents using PyPDF in mentioned below:# pdf_merging.py from PyPDF2 import PdfFileReader, PdfFileWriter def pdfmerger(paths, output):     pdfwrite = PdfFileWriter()     for path in paths:         pdfread = PdfFileReader(path)         for page in range(pdfread.getNumPages()):             # Add each page to the writer object             pdfwrite.addPage(pdfread.getPage(page))     # Write out the merged PDF     with open(output, 'wb') as out:         pdfwrite.write(out) if __name__ == '__main__':     paths = ['document-1.pdf', 'document-2.pdf']     pdfmerger(paths, output='merged.pdf')Here we have created a function pdfmerger() which takes a number of inputs and a single output. Then we created a PdfFileReader() object for each PDF path and looped over the pages, added each page to the write object. Finally, using the write() function the object’s contents are written to the disk.PyPDF2 makes the process of merging simpler by creating the PdfFileMerger class.Code for merging two documents using PyPDF2—# pdf_merger2.py import glob from PyPDF2 import PdfFileMerger def merger(output_path, input_paths):     pdfmerge = PdfFileMerger()     file_handles = []     for path in input_paths:         pdfmerge.append(path)     with open(output_path, 'wb') as fileobj:         pdfmerge.write(fileobj) if __name__ == '__main__':     paths = glob.glob('d-1.pdf')     paths.sort()     merger('d-2.pdf', paths)The PyPDF2 makes it simpler in the way that we don’t need to loop the pages of each document ourselves.  Here, we created the object pdfmerge and looped through the PDF paths. The PyPDF2 automatically appends the whole document. Finally, we write it out.Let’s perform the opposite of merging now!Splitting PDFsThe PyPDF2 package has the ability to split up a single PDF into multiple PDFs. It allows us to split pages into different PDFs. Suppose we have a set of scanned documents in a single PDF and we need to separate the pages into different PDFs as per requirement, we can simply use Python to select pages we want to split and get the work done.Code for splitting a single PDF into multiple PDFs—# pdf_splitter.py import os from PyPDF2 import PdfFileReader, PdfFileWriter def splitpdf(path):     fname = os.path.splitext(os.path.basename(path))[0]     pdf = PdfFileReader(path)     for page in range(pdf.getNumPages()):         pdfwrite = PdfFileWriter()         pdfwrite.addPage(pdf.getPage(page))         outputfilename = '{}_page_{}.pdf'.format(             fname, page+1)         with open(outputfilename, 'wb') as out:             pdfwrite.write(out)         print('Created: {}'.format(outputfilename)) if __name__ == '__main__':     path = 'document-1.pdf'     splitpdf(path)Here we have imported the PdfFileReader and PdfFileWriter from PyPDF2. Then we created a function called splitpdf() which accepts the path of PDF we want to split. The first line of the function takes the name of the input file. Then we open the PDF and create a read object. Using the read object’s getNumPages(), we loop over all the pages.In the next step, we created an instance of PdfFileWriter inside the for loop. Then, we created a PDF write instance and added each page to it for each of the pages in the PDF input. We also created a unique filename using the original filename + the word ‘page’ + the page number + 1.Once we are done with running the script, we will have each of the pages of the input PDF split into multiple PDFs. Now let us learn how to add a watermark to a PDF and keep it secured.Adding Overlays/WatermarksAn image or superimposed text on selected pages in a PDF document is referred to as a Watermark. The Watermark adds security features and protects our rational property like images and PDFs. Watermarks are also called overlays.The PyPDF2 allows us to watermark documents. We just need to have a PDF which will consist of our watermark text, image or signature.Code for adding a watermark in a PDF—# watermarker.py from PyPDF2 import PdfFileWriter, PdfFileReader def watermark(inputpdf, outputpdf, watermarkpdf):     watermark = PdfFileReader(watermarkpdf)     watermarkpage = watermark.getPage(0)     pdf = PdfFileReader(inputpdf)     pdfwrite = PdfFileWriter()     for page in range(pdf.getNumPages()):         pdfpage = pdf.getPage(page)         pdfpage.mergePage(watermarkpage)         pdfwrite.addPage(pdfpage)     with open(outputpdf, 'wb') as fh:         pdfwrite.write(fh) if __name__ == '__main__':     watermark(inputpdf='document-1.pdf',               outputpdf='watermarked_w9.pdf',               watermarkpdf='watermark.pdf')The output of the code will look like— There are three arguments of the function watermark(): inputpdf: The path of the PDF that is to be watermarked. outputpdf: The path where the watermarked PDF will be saved. watermarkpdf: The PDF which contains the watermark.Firstly, we extract the PDF page which contains the watermark image or text and then open that PDF page where we want to give the desired watermark.Using the inputpdf, we create a read object and using the pdfwrite, we create a write object to write out the watermarked PDF and then iterate over the pages.Next, we call the page object’s mergePage and apply the watermark and add that to the write object pdfwrite.When the loop terminates, the watermarked PDF is written out to the disk and it’s done!Encrypting a PDFIn the PDF world, the PyPDF2 package allows an owner password which gives the user the advantage to work as an administrator. The package also provides the user password which allows us to open the document upon entering the password.The PyPDF2 basically doesn’t permit any allowances on any PDF file yet it allows the user to set the owner password and user password.Code to add a password and add encryption to a PDF—# pdf_encrypt.py from PyPDF2 import PdfFileWriter, PdfFileReader def encryption(inputpdf, outputpdf, password):     pdfwrite = PdfFileWriter()     pdfread = PdfFileReader(inputpdf)     for page in range(pdfread.getNumPages()):         pdfwrite.addPage(pdfread.getPage(page))     pdfwrite.encrypt(user_pwd=password, owner_pwd=None,                       use_128bit=True)     with open(outputpdf, 'wb') as fh:         pdfwrite.write(fh) if __name__ == '__main__':     encryption(inputpdf='document-1.pdf',                   outputpdf='document-1-encrypted.pdf',                   password='twofish')We declare a  function named encryption() with three arguments—the input PDF path, the output PDF path and the password that we want to keep. Then we create one read object pdfread and one write object pdfwrite. Now we loop over all the pages and add them to the write object since we need to encrypt the entire document.Finally, we call the encrypt() function which accepts three parameters—the user password, the owner password and the whether or not to use 128-bit encryption. The PDF  will be encrypted to 40-bit encryption if the argument use128bit is set to false. Also if the owner password is set to none, then it will be set to user password automatically.Reading the Table data from PDFSuppose you want to work with the Table data in Pdf, you can use tabula-py to read tables in a PDF. To install tabula-py, run:pip install tabula-pyCode to extract simple Text from pdf using PyPDF2:import tabula # readinf the PDF file that contain Table Data # you can find the pdf file with complete code in below # read_pdf will save the pdf table into Pandas Dataframe df = tabula.read_pdf("document.pdf") # in order to print first 5 lines of Table df.head()If you PDF file contains Multiple Tabledf = tabula.read_pdf("document.pdf",multiple_tables=True)If you want to extract Information from the specific part of any specific page of PDFtabula.read_pdf("document.pdf", area=(126,149,212,462), pages=1)If you want the output into JSON Formattabula.read_pdf("offense.pdf", output_format="json")Exporting PDF into ExcelSuppose you want to export a PDF into Excel, you can do so by writing the following code and convert the PDF Data into Excel or CSV.tabula.convert_into("document.pdf", "document_testing.xlsx", output_format="xlsx")Let us sum up what we have learned in the article:Extraction of data from a PDFRotate pages in a PDFMerge PDFs into one PDFSplit a PDF into many PDFsAdd watermarks or overlays in a PDFAdd password or encryption to a PDFReading table from PDFExporting PDF into Excel or CSVAs you have seen, PyPDF2 is one of the most useful tools available in Python. The features of PyPDF2 makes life easier whether you are working on a large project or even when you quickly want to make some changes to your PDF documents. Learn more about such libraries and frameworks as KnowledgeHut offers Python Certification Course for Programmers, Developers, Jr./Sr Software Engineers/Developers and anybody who wants to learn Python.
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How to Work With a PDF in Python

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Web Development Using PHP And MySQL

PHP (or PHP Hypertext Preprocessor) is a server-side scripting language that is used to create dynamic web pages that can interact with databases. It is a widely-used open source language that is specifically used for web application development and can be embedded within HTML. Why PHP? The distinguishing feature of PHP is that the scripting code is executed on the server, which generates HTML that is sent back to the client. The client receives the result of executing the script without knowing the underlying code. Developers can configure the web server to process all the HTML files (containing the PHP script). PHP course is easy to learn for any newcomer, but also offers advanced programming features. Using PHP with a database system PHP, as a scripting language, is popular among web developers because of its ability to interact with database systems including Oracle and MySQL. This article discusses the use of PHP scripting language with the MySQL database. Any website can require a variety of data or information to display and to retrieve them from the database. This can include display of a simple list to the running of the website based on data stored in the database. Listed below are some examples where PHP and MySQL can be used together: • Digital Ad banners, where the PHP script can be used to retrieve a digital banner from the database, which then selects a random banner from its table records and sends it back to the calling script. The PHP script can also maintain a count of banner views and clicks from the website. • Internet forums or digital boards, which use PHP and MySQL to store and retrieve user messages. • Website designing, where the design of an entire website can be changed using a couple of PHP scripts, instead of changing and uploading each web page. The PHP script can access the MySQL database to retrieve all information about the web page. Setting up the MySQL database The procedure of setting up the MySQL database varies according to the host. Every database would require a user name and password, in order to access the database. Database administration can be done using PHP scripts or using a program like PHPMyAdmin. The next step is to create the database tables for storing the website information. Creating a database table using PHPMyAdmin is also simple. Alternatively, one can create and configure the entire database using the following PHP script: CREATE TABLE tablename { Fields } Where the Fields are coded as fieldname type(length) extra_info Example: first varchar(15) NOT NULL The following command is used in the PHP script to connect to the MySQL database: mysql_connect(localhost,$username,$password); where: • localhost is the server address on which the web site is running, • $username is the user name for the database access • $password is the password for the database access Executing PHP commands After configuring and connecting to the MySQL database, you can start executing PHP commands on the server. Following are the 2 methods of executing a PHP command: • Entering the command in PHP using the following syntax: Mysql_query($query) This form of command can be used to repeat the command simply by changing the variable. • Defining the command as a variable. The result of the operation will be assigned to the variable. Data input and output Inserting data using PHP is identical to the procedure of data input using HTML pages. The advantage of using PHP is that the script does not need to be changed for each new piece of input data. Users can also input their own data on the web page. Following is an example of an HTML page with textboxes that can be used to enter data in a form: Alternatively, you can use variables to input information into the database. Example: $first=$_POST[‘first’]; $last=$_POST[‘last’]; $phone=$_POST[‘phone’]; $mobile=$_POST[‘mobile’]; $fax=$_POST[‘fax’]; $email=$_POST[’email’]; $web=$_POST[‘web’]; … $query = “INSERT INTO contacts VALUES (”,’$first’,’$last’,’$phone’,’$mobile’,’$fax’,’$email’,’$web’)”; mysql_query($query); This script is saved in the insert.php file, which can be called from the HTML form. Using this method, data entered in the web page form is stored in the defined variables, which are then passed to the PHP. To display (or output) the entered data using PHP, you can use the following MySQL command with the result assigned to the variable. $query=”SELECT * FROM contacts”; $result=mysql_query($query); PHP provides 2 submission methods, GET and POST to get the data submitted by the form into your PHP script. GET method displays the variables and the data in the page address, while they are invisible in the POST method. For example, a script can be created that will display different web pages depending on the clicked link. yourpage.php?user=david (to show David’s page) yourpage.php?user=tom (to show Tom’s page)
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Web Development Using PHP And MySQL

PHP (or PHP Hypertext Preprocessor) is a server-si... Read More

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