Python List is one of the built-in data types in Python designed to store collections of data.

List Features

• Ordered – List maintains the order of elements.
• Mutable – Items can be changed after creation.
• Allow duplicates – Duplicate values can be stored in Python List.

Create a List

You can create a list by placing elements inside square brackets [] , separated by commas.

# create a python list
data = [1, 2, 3]
print(data)

# Output:[1, 2, 3]

You also can place different types of elements in a Python List.

# create a python list that contains different types of items
data = [1, 2.0, "this is a test"]
print(data)

# Output:[1, 2.0, "this is a test"]

You also can use list() function to convert an iterables (strings, dictionaries, tuples, etc.) to a list.

# convert a string to list
text = "this is a text"
data = list(text)
print(data)

# Output: ['t', 'h', 'i', 's', ' ', 'i', 's', ' ', 'a', ' ', 't', 'e', 'x', 't']

List is Empty?

[] or list() will create an empty list, its length is 0. To check if a list is empty or not, we can use if statement.

# create an empty list
data = []
if data:
    print("data list is not empty")
else:
    print("data list is empty")

List Length

Python len() method returns the number of elements in the specified list.

my_list = [1, 2, 3, 4, 5]
length = len(my_list)
print(length)
# Output: 5

Accessing Elements

You can use index to access individual element, the index is in [0, len(list)-1]

my_list = [1, 2, 3, 4, 5]
print(my_list[0])  # Output: 1

index = 0: the first element

index = len(list)-1: the last element

index = -1: the last element

Slicing Elements

Extracting a subset of elements using slicing.

my_list = [1, 2, 3, 4, 5]
print(my_list[1:4])  # Output: [2, 3, 4]

Adding Elements

You can use List append() method to add an element to the end of a Python List.

fruits = ['apple', 'banana', 'orange']
print('Original List:', fruits)

# using append method 
fruits.append('cherry')

print('Updated List:', fruits)

Changing Items

You can use index to change an item in a python list.

Changing a Single List Item

You can change a single item in a list by accessing the item using its index and assigning a new value to it.

my_list = [1, 2, 3, 4, 5]
my_list[2] = 10
print(my_list)
# Output: [1, 2, 10, 4, 5]

Changing Multiple List Items

You can change multiple items in a list using slicing and assignment.

my_list = [1, 2, 3, 4, 5]
my_list[1:4] = [20, 30, 40]
print(my_list)
# Output: [1, 20, 30, 40, 5]

Remove an Item From a List

You can use List remove() method to remove an item form a list.

numbers = [2,4,7,9]

# remove 4 from the list
numbers.remove(4)

print(numbers) 

# Output: [2, 7, 9]

Iterating Through a List

You can use a for loop to iterate over the elements of a list.

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

# iterate through the list
for fruit in fruits:
    print(fruit)

Output:

apple
banana
orange