Explain List in python with examples

In this post, we will learn Python list in detail with very basic explanations and examples. So let’s begin with the very basic question ‘What is a list in Python’.

What is the List in Python?

The list is one type of built-in data structure in python and it is used to store an ordered collection of items in a single variable.

Create a list

To create a list in Python write comma-separated values inside a square bracket ([ ]) or you can use the list() function to create a list in Python.

Example:

my_list = [1,4,6,8,9]
print(my_list)

Output:

[1, 4, 6, 8, 9]

Create a list using list() function

Example:

num_list = list(range(1,11))
print(num_list)

Output:

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

Mixed list

You can store anything in a list (like int, float, string, boolean, tuples, list, dictionary, etc..,)

Example:

mixed_list = ["first name",34.5,45,True]
print(mixed_list)

Output:

['first name', 34.5, 45, True]

Access elements of list

You can access any values inside the list using indexing in python.

Example:

My_string = ["saurabh","ibrahim","ram","syam"]
# indexing starts from 0

# "saurabh"  ---> at 0 index
# "ibrahim"  ---> at 1 index
# "ram"  ---> at 2 index
# "syam"  ---> at 3 index   likewise

print(My_string[0])
print(My_string[3])
print(My_string[1])

# you can also use negative indexing.
# negative indexing starts from -1

# "syam"  ---> at -1 index
# "ram"  ---> at -2
# "ibrahim"  ---> at -3
# "saurabh"  ---> at -4  likewise

print(My_string[-1])
print(My_string[-3])

Output:

saurabh
syam
ibrahim
syam
ibrahim

Similarly, you can also use slicing and step-argument in the list.

Create empty list

There are two ways to create an empty list in python.

1. using square bracket
2. using list() function

Example:

# using square breaket
my_list1 = []  
# using list function
my_list2 = list()

print(my_list1) # []
print(my_list2) # []

Output:

[]
[]

Add data in list

There are three methods used to add data to the list and they are.

1. append()
2. insert()
3. extend()

append() method

append() method is used to add data at the end of the list.

Syntax –> list_name.append(data)

Example:

my_num1 = [1,2,3]
print(my_num1)

my_num1.append(4)  # add 4
print(my_num1)

my_num1.append(45) #add 45
print(my_num1)

Output:

[1, 2, 3]
[1, 2, 3, 4]
[1, 2, 3, 4, 45]

insert() method

insert() method is used to add data at a specific index in the list.

Syntax –> list_name.insert(index_value, data)

Example:

my_data = ['harshit','rahul','raj']
print(my_data)

my_data.insert(1,'saurabh')
print(my_data)

my_data.insert(0,'allinpython.com')
print(my_data)

Output:

['harshit', 'rahul', 'raj']
['harshit', 'saurabh', 'rahul', 'raj']
['allinpython.com', 'harshit', 'saurabh', 'rahul', 'raj']

extend() method

extend() method is used to add the whole data of the list into another list.

syntax –> list_name_1.extend(list_name_2)

Example:

my_data1 = ['A','B','C','D']
my_data2 = ['E','F','G','H']

my_data1.extend(my_data2)

print(my_data1)

Output:

['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H']

Delete data from list

there are two methods and one operator (keyword) use to delete data from the list and they are.

1. pop() method
2. remove() method
3. del keyword

pop() method

pop() method is used to remove data at the end of the list.

Syntax –> list_name.pop()

Example:

my_data1 = ['A','B','C','D']
print(my_data1)

my_data1.pop()
print(my_data1)

my_data1.pop()
print(my_data1)

Output:

['A', 'B', 'C', 'D']
['A', 'B', 'C']
['A', 'B']

NOTE: In the pop method if you write the index value of data then the pop method will delete data at that particular index.

example: mydata1.pop(0) {remove data at index 0}

remove() method

remove method is used to remove specific data from the list.

Syntax –> list_name.remove(your_data)

Example:

my_list = ['harshit','rahul','raj']
print(my_list)

my_list.remove('raj')
print(my_list)

Output:

['harshit', 'rahul', 'raj']
['harshit', 'rahul']

del keyword

del keyword is used to delete data at a specific index in a list and the del keyword is also used to delete the whole list.

Syntax –> del list_name[index_value]

Example:

my_data2 = ['E','F','G','H']
print(my_data2)

del my_data2[1] #remove F
print(my_data2)

Output:

['E', 'F', 'G', 'H']
['E', 'G', 'H']

Loop in list

for loop:

fruits = ['orange', 'apple', 'pear']

for i in fruits:
    print(i)

Output:

orange
apple
pear

while loop:

fruits = ['orange', 'apple', 'pear']

i = 0
while i < len(fruits):
    print(fruits[i])
    i+=1

Output:

orange
apple
pear

List inside list

matrix  = [[1,2,3],[4,5,6],[7,8,9]]
print('list inside list: ',matrix)  # this type of list is known as 2d list 

print('list elments: ',matrix[0])
print('elements of list inside list: ',matrix[0][1])

print('loop in 2d list')

for i in matrix:
    for j in i:
        print(j)

Output:

list inside list:  [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
list elments:  [1, 2, 3]
elements of list inside list:  2
loop in 2d list
1
2
3
4
5
6
7
8
9

Methods of list

1. count()	2. sort()	3.index()
4. reverse()	5. clear()	6. copy()
7. append()	8. insert()	9. extend()
10. pop()	11. remove()	12. len() function

Count() Method

the count() method returns the number of times specified items appear in a list.

cars = ['Toyota','Chevrolet','Renault','Toyota']

print(cars.count('Toyota'))

Output:

2

sort() Method

The sort() method sorts the list in ascending, descending, or alphabetical order.

# ascending order

numbers = [5,2,7,1,3]
numbers.sort()
print(numbers)   # output: [1, 2, 3, 5, 7]

alphabates = ['A','F','B','K','D']
alphabates.sort()
print(alphabates)  #output: ['A', 'B', 'D', 'F', 'K']


# descending order 

num2 = [1,5,2,6,8]
num2.sort(reverse=True)
print(num2)  # output: [8, 6, 5, 2, 1]


alphabates2 = ['A','F','B','K','D']
alphabates2.sort(reverse=True)
print(alphabates2) # output: ['K', 'F', 'D', 'B', 'A']

Output:

[1, 2, 3, 5, 7]
['A', 'B', 'D', 'F', 'K']
[8, 6, 5, 2, 1]
['K', 'F', 'D', 'B', 'A']

Sorted() Function

You can also use sorted() function to sort the list.

The main difference between the sort() method and the sorted() function is that the sorted() function returns a new sorted list but the sort() method sorts in the same list.

# ascending order
numbers = [5,2,7,1,3]
rev_num = sorted(numbers)
print(rev_num)

# descending order 
num2 = [1,8,5,9,3]
rev_num2 = sorted(num2,reverse=True)
print(rev_num2)

Output:

[1, 2, 3, 5, 7]
[9, 8, 5, 3, 1]

index() Method

The index() method returns the index value of the first occurs specified item of the list.

bikes = ['Suzuki','TVS','Hero','Suzuki']
print(bikes.index('Suzuki'))

Output:

0

reverse() Method

the reverse() method is used to reverse the list.

bikes = ['Suzuki','TVS','Hero','Yamaha']
bikes.reverse()
print(bikes)

Output:

['Yamaha', 'Hero', 'TVS', 'Suzuki']

clear() Method

The clear() method is used to clear (or empty) the list.

num = [1,2,3,4,5]
num.clear()
print(num)

Output:

[]

copy() Method

the copy() method is used to create a copy of the list.

l1 = [2,3,5,7,11,13]
l2 = l1.copy()

print(l2)

Output:

[2, 3, 5, 7, 11, 13]

Hope this post helped you to learn the list in python. -thank you.