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Lecture 04: Lists & Tuples

In Python, lists and tuples are used to store multiple items in a single variable.

1. Lists

A list is an ordered, mutable (changeable) collection of items. Lists are defined using square brackets [].

motorcycles = ["honda", "yamaha", "suzuki"]

Accessing Elements

Lists are zero-indexed:

print(motorcycles[0])   # Output: honda
print(motorcycles[-1])  # Output: suzuki (last element)

Modifying Elements

motorcycles[0] = "ducati"
print(motorcycles)  # Output: ["ducati", "yamaha", "suzuki"]

Adding Elements

  • append(): Adds an item to the end of the list.
  • insert(): Adds an item at a specific index.
motorcycles.append("honda")        # Adds to the end
motorcycles.insert(1, "harley")   # Inserts at index 1

Removing Elements

  • del: Deletes an item at a specific index (permanent).
  • pop(): Removes and returns the last item (or index specified).
  • remove(): Removes the first occurrence of a value.
del motorcycles[0]       # Deletes the first element
popped_bike = motorcycles.pop()  # Removes and returns last element
motorcycles.remove("yamaha")     # Removes by value

2. Organizing Lists

  • sort(): Sorts the list permanently in alphabetical/numerical order.
  • sorted(): Returns a sorted copy of the list, leaving the original list unchanged.
  • reverse(): Reverses the order of the list permanently.
  • len(): Returns the length (number of items) in the list.
cars = ["bmw", "audi", "toyota", "subaru"]
cars.sort()          # Permanent sort
print(sorted(cars))  # Temporary sort
cars.reverse()       # Permanent reverse
print(len(cars))     # 4

3. Tuples

A tuple is an ordered, immutable (unchangeable) collection of items. Tuples are defined using parentheses ().

dimensions = (200, 50)
print(dimensions[0])  # 200

# dimensions[0] = 250  # TypeError! You cannot modify elements in a tuple
  • If you need to define a tuple with only one element, you must include a trailing comma: single_tuple = (3,).

4. Packing and Unpacking

You can pack values into a tuple or list, and unpack them into individual variables.

# Packing
coordinates = (10, 20)

# Unpacking
x, y = coordinates
print(x)  # 10
print(y)  # 20

🧠 Try It Yourself

  1. Create a list of 5 movies. Add one movie to the end, insert one in the middle, and pop the last one. Print the list length.
  2. Create a tuple containing three items of food. Try to change one of the foods and look at the error.