Python List

1. Creating a List

empty_list = []
numbers = [1, 2, 3, 4, 5]
mixed = [10, "Python", True, 5.5]

print(empty_list)
print(numbers)
print(mixed)

Lists are ordered, mutable collections that can store heterogeneous data.

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2. Accessing List Elements (Indexing)

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

print(fruits[0])   # First element
print(fruits[-1])  # Last element

Lists support both positive and negative indexing.

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3. Slicing Lists

numbers = [0, 1, 2, 3, 4, 5]

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

Extracts a sublist using slice notation.

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4. Modifying List Elements

items = ["pen", "pencil", "eraser"]
items[1] = "marker"

print(items)  # Output: ['pen', 'marker', 'eraser']

Lists are mutable and allow in-place updates.

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5. Adding Elements to a List

numbers = [1, 2, 3]

numbers.append(4)
numbers.insert(1, 10)

print(numbers)  # Output: [1, 10, 2, 3, 4]

• append() adds at the end

• insert() adds at a specific index

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6. Removing Elements from a List

data = [10, 20, 30, 40]

data.remove(20)
last = data.pop()

print(data)  # Output: [10, 30]
print(last)  # Output: 40

• remove() deletes by value

• pop() deletes by index (default last)

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7. List Length and Membership

values = [5, 10, 15]

print(len(values))       # Output: 3
print(10 in values)      # Output: True
print(100 not in values) # Output: True

Used for validation and condition checks.

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8. List Iteration

cities = ["New York", "London", "Tokyo"]

for city in cities:
    print(city)

Lists are iterable and commonly used with loops.

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9. List Comprehension

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

Concise way to generate lists using expressions.

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10. Sorting and Reversing Lists

numbers = [4, 1, 3, 2]

numbers.sort()
print(numbers)  # Output: [1, 2, 3, 4]

numbers.reverse()
print(numbers)  # Output: [4, 3, 2, 1]

Used to reorder list elements in-place.

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