List

 

Introduction

In Python, a List is a collection that allows us to store multiple items in a single variable. Lists are one of the most commonly used data types because they are flexible, ordered, and mutable.

Example:

fruits = ["apple", "banana", "cherry"]
print(fruits)

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Features of Lists

• Ordered: Items have a defined order.

• Mutable: We can change items after creating a list.

• Allow duplicates: Lists can store repeated values.

• Store multiple data types: A single list can hold strings, numbers, and even other lists.

Example:

mixed = [10, "Python", 3.14, True, [1, 2, 3]]
print(mixed)

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Creating a List

# Empty list
empty_list = []

# List of numbers
numbers = [1, 2, 3, 4, 5]

# List of strings
languages = ["Python", "C", "Java"]

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Accessing List Items

We can access items using indexing and slicing.

fruits = ["apple", "banana", "cherry"]

print(fruits[0])   # apple
print(fruits[-1])  # cherry
print(fruits[0:2]) # ['apple', 'banana']

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Modifying a List

fruits = ["apple", "banana", "cherry"]
fruits[1] = "mango"
print(fruits)  # ['apple', 'mango', 'cherry']

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Adding Items

fruits = ["apple", "banana"]
fruits.append("cherry")        # add at end
fruits.insert(1, "mango")      # add at index
print(fruits)

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Removing Items

fruits = ["apple", "banana", "cherry"]

fruits.remove("banana")  # remove by value
fruits.pop(0)            # remove by index
del fruits[0]            # delete specific item
print(fruits)

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List Functions and Methods

Some common ones are:

• len(list) → length of list

• min(list), max(list) → smallest/largest element

• sum(list) → sum of numeric values

• list.sort() → sort list

• list.reverse() → reverse list

Example:

numbers = [5, 2, 9, 1]
numbers.sort()
print(numbers)   # [1, 2, 5, 9]

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Looping Through a List

fruits = ["apple", "banana", "cherry"]

for fruit in fruits:
    print(fruit)

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List Comprehension

A short way to create lists.

squares = [x**2 for x in range(5)]
print(squares)  # [0, 1, 4, 9, 16]

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Nested Lists

Lists inside another list.

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

                                               

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Conclusion

Python Lists are powerful and versatile. They allow easy data storage, modification, and access. Understanding lists is essential for mastering Python programming.