Python List : Adding element to List

Adding an element to the list

We can add elements to the list using append, insert and extend functions.

#Initializing empty list

alist = [] 

Append function

It is used to add elements at the end of the list.
Append function takes only one argument at a time i.e using append function we can add only one element at a time.

#Adding element in the list using append function

alist.append(1)

alist.append(3)

alist.append(5)

print('List after addition of 3 elements :  ', alist ) 

Output :

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Insert function

It is used to add an element at the specified index position of the list.

#Adding an element at a specific index using insert function. 

alist.insert(1,2)

print('List after performing insert operation :  ' , alist)

#Here we are adding element 2 at index position 1

Output :

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Extend function

It is used to add a sequence of elements to the list.
This function adds elements at the end of a list.
Extend function takes a list of elements as the argument.
#Adding multiple elements to the list
alist.extend( [ 4 , 'python' , 8.97 , (91,90,89) ] )
print('List after performing extend operation :  ' , alist)
#Here we are adding elements 4 , ' python ',8.97 and tuple (91,90,89)

Output :

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Python Lists : Creating List

List

The list is  simplest data structure in python which is used to store a collection of data.
The list is a collection of items like String, Numbers, Lists, Tuples, Dictionaries.
Lists are enclosed in square brackets [] .
Each value in the list is assigned to the index value.
An index value of the list is start from 0 .
Each item in list is separated by comma(,) .
List is Mutable data structure which means we can add , remove ,  replace , append the elements of list whenever we want.

Example : alist = [ 2 , 3 , 4 , 'a' , 7.67 , 'python' ]

How to create List...?

#Creating empty list
#Creating empty list means creating object of list data stucture with no values.
alist = []
print('Initialize empty list :  ' , alist )

#Creating a list of strings
alist = ['hii','this','is','Python']
print('List with string values :  ' , alist )

#Creating a list of integers
alist = [ 1 ,3, 5 , 7]
print('List with integer values :  ' , alist )
#You can also create a list with float , long , complex type integers

#Creating list having mixed type of values(stings , numbers)
alist = [ 345 , 'python' , 6.9836 , 218748682686836753656 , 'program' , 6+8j ]
print('List with mixed type of values :  ' , alist )

#Creating list with list type data structure
#List with lst type of items also called as nested lists or multidimensional list.
alist = [[3,4,5],['a','b','c'],[3.67,9,'hello']]
print('Multi-Dimensional List :  ' , alist )

#Creating list with the use of tuples
alist = [(4,5,6),('a','v','d'),(3,7,1)]
print('List with the use of tuples :  ' , alist )

#Creating list with the use od dictionaries
alist = [{1:'Python' , 2 :'Programming'},{'a' : 97 , 'b' :98 }]
print('List with the use of dictionaries :  ' , alist )

Output :

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A list may contain duplicate values with their distinct positions .
List store its element according to the index positions so we can store the same element multiple index positions, this can duplicate that element in a list.
If the list contains duplicate elements then that duplicate elements have different index positions.

#Creating a list with duplicate values
alist = [ 'a', 1 ,3 , 3 , 7 ,'a' , 5 , 7]
print('List with duplicate values :  ' , alist )

Output :

In above example ,three elements of list have duplicates
element 'a' have two index positions i.e. 0 and 5 .
element 3 have two index positions i.e. 2 and 3 .
element 7 also havetwo index positions i.e. 4 and 7 .
Because of different index positioning these elements considered as distinct elements not as same element .