Python List Data Type

What is a List?

A list in Python is an ordered, mutable collection of items. Lists can store different types of data such as numbers, strings, or even other lists.

Examples:

fruits = ["apple", "banana", "cherry"]
numbers = [1, 2, 3, 4, 5]
mixed = [1, "hello", 3.14, True]

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Creating a List

You can create a list using square brackets []:

my_list = [10, 20, 30]
empty_list = []

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Accessing Elements

Lists are indexed, starting at 0. You can access elements using their index:

animals = ["cat", "dog", "elephant"]

print(animals[0])   # "cat"
print(animals[1])   # "dog"
print(animals[-1])  # "elephant" (last item)

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Modifying a List

Lists are mutable, meaning you can change their contents:

colors = ["red", "blue", "green"]
colors[1] = "yellow"
print(colors)  # ["red", "yellow", "green"]

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Common List Operations

nums = [1, 2, 3]

# Add items
nums.append(4)        # [1, 2, 3, 4]
nums.insert(1, 10)    # [1, 10, 2, 3, 4]

# Remove items
nums.remove(10)       # [1, 2, 3, 4]
nums.pop()            # Removes last → [1, 2, 3]

# Length
print(len(nums))      # 3

# Concatenation
print(nums + [4, 5])  # [1, 2, 3, 4, 5]

# Repetition
print(nums * 2)       # [1, 2, 3, 1, 2, 3]

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Looping Through a List

fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
    print(fruit)

Output:

apple
banana
cherry

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List Slicing

Lists support slicing just like strings:

letters = ["a", "b", "c", "d", "e"]
print(letters[1:4])   # ['b', 'c', 'd']
print(letters[:3])    # ['a', 'b', 'c']
print(letters[::2])   # ['a', 'c', 'e']

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Nested Lists

Lists can contain other lists:

matrix = [[1, 2], [3, 4], [5, 6]]
print(matrix[0])     # [1, 2]
print(matrix[1][1])  # 4

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Useful List Methods

numbers = [3, 1, 4, 1, 5]

print(min(numbers))   # 1
print(max(numbers))   # 5
print(sum(numbers))   # 14

numbers.sort()
print(numbers)        # [1, 1, 3, 4, 5]

numbers.reverse()
print(numbers)        # [5, 4, 3, 1, 1]

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Summary

• Lists are ordered, mutable collections of items.
• Support indexing, slicing, and iteration.
• Can hold different types of data.
• Provide many built-in methods (append, remove, sort, etc.).

Lists are one of the most versatile and commonly used data types in Python!