Hi There, In this post we’ll see python lists and lists methods

Python List

• A list is a collection which is ordered and changeable. In Python lists are written with square brackets.

• Example List:

    my_list = ['Tony', True, 24, 'Hi there']
  

List Methods

what is List in Python

• List is a collection data type, which can store all datatype values, List is ordered and changeable. and it allows duplicate members.

• Example List

    my_list = [1, 'Hi', True, [1, 2], {1 : A}]
  

List Methods

List append()

• The method append() appends a passed obj into the existing list.

• Syntax

    list.append(obj) # Takes only one argument
  

• append() method takes only one argument
• append() method does not return any value but updates the existing list.

• Example Usage:

    a_list = [1, 2, 3, 4]
    a_list.append(5) #Appending 5 into a_list
    print(a_list)
  

• OutPut for above Example code [1, 2, 3, 4, 5]

List extend()

• The method extend() appends the contents of seq to list.

• Syntax

    list.extend(seq) # Takes only one argument
  

• extend() method takes list of elements or a string
• extend() method does not return any value but add the content to existing list.

• Example Usage:

    a_list = [1, 2, 3, 4]
    a_list.extend([5 ,6 , 7, 8]) #Extending a_list with 5, 6, 7, 8 sequence
    print(a_list)
  

• OutPut for above Example code [1, 2, 3, 4, 5, 6, 7, 8]

List insert()

• The method insert() method inserts object into list at given index.

• Syntax

    list.insert(index, obj) # Takes two arguments
  

• insert() method takes two arguments i.e index and value
• insert() does not return any value but it inserts the given element at the given index.

• Example Usage:

    a_list = ['A', 'C', 'D']
    a_list.insert(1, 'B') #Inserting 'B' at the 1st Index in a_list
    print(a_list)
  

• OutPut for above Example code [‘A’, ‘B’, ‘C’, ‘D’]

List clear()

• The method clear() method deletes all items in list.

• Syntax

    list.clear() # Takes no arguments
  

• clear() method does not take any arguments
• clear() method does not return any value but deletes all items in a list.

• Example Usage:

    a_list = [1, 2, 3, 4]
    a_list.extend() #Deleting items in a_list using clear() method
    print(a_list)
  

• OutPut for above Example code []

List pop()

• The method pop() method removes and returns last object or obj from the list.

• Syntax

    list.pop() #Takes one optional argument
  
    or
  
    list.pop(1) #Takes one optional argument
  

• pop() method takes one optional argument
• pop() method returns last object or obj from the list.

• Example 1 Usage without argument:

    a_list = [1, 2, 3, 4]
    a_list.pop() #Deleting last item in a_list using pop() method
    print(a_list)
  

• OutPut for above Example code [1, 2, 3]

• Example 2 Usage without argument:

    a_list = [1, 2, 3, 4]
    a_list.pop() #Deleting item 3 by providing index of 3.
    print(a_list)
  

• OutPut for above Example code []

List remove()

• The method remove() removes a passed value from the existing list.

• Syntax

    list.remove(item) # Takes only one argument
  

• remove() method takes only one argument
• remove() method does not return any value but removes given item from the existing list.

• Example Usage:

    a_list = [1, 2, 3, 4]
    a_list.remove(3) #removing 3 from a_list
    print(a_list)
  

• OutPut for above Example code [1, 2, 4]

List index()

• The method index() finds the index of a passed value from the list.

• Syntax

    list.index(item) # Takes three  arguments.
  

• index() method takes three arguments two optional.
• index() method returns index of the passed value from the list.

• Example Usage:

    a_list = [1, 2, 3, 4]
    res = a_list.index(3) #finding 3 index from a_list
    print(res)
  

• OutPut for above Example code 2

• Example Usage With two arguments:

    a_list = [1, 2, 3, 4, 4 , 1]
    a_list.index(1, 1)
    print(a_list)
  

• OutPut for above Example code 5 #index of value 1 after the index 1

List count()

• The method count() appends a passed obj into the existing list.

• Syntax

    list.count(obj) # Takes only one argument
  

• count() method takes only one argument
• count() method does not return any value but updates the existing list.

• Example Usage:

    a_list = [1, 2, 3, 4, 3, 3, 3]
    a_list.count(3) #Finding no. of occurances of 3 in a_list
    print(a_list)
  

• OutPut for above Example code 4

List reverse()

• The method reverse() reverses the items the list.

• Syntax

    list.reverse() # Takes no argument
  

• reverse() method takes no argument
• reverse() method does not return any value but updates the existing list by reversing the items.

• Example Usage:

    a_list = [1, 2, 3, 4, 5]
    a_list.reverse() #reversing the items in a_list
    print(a_list)
  

• OutPut for above Example code [5, 4, 3, 2, 1]

List sort()

• The method sort() reverses the items the list.

• Syntax

    list.reverse() # Takes no argument
  

• sort() method takes no argument
• sort() method does not return any value but updates the existing list by sorting the items.

• Example Usage:

    a_list = [1, 5, 4, 2, 3]
    a_list.sort() #sorting the items in a_list
    print(a_list)
  

• OutPut for above Example code [1, 2, 3, 4, 5]

String Method

join()

• join() used to join the items in a list or a iterable

• Example Usage:

    a_list = ['A', 'B', 'C', 'D']
    ','.join(a_list)#Joining the items in the list with a ,
    print(a_list)
  

• OutPut for above Example code ‘A,B,C,D’