Lists and Tuples

Friendly intro

Welcome to PyVerse! Today we'll learn about two super-useful ways to store many values in one place: lists and tuples. Think of a list like a backpack you can open, rearrange, and add things to. A tuple is more like a sealed box: you can look inside, but you don't change what's in it.

What you will learn

What lists and tuples are
How to create them
How to get items from them
How to add/remove items (lists) and why tuples can't change
When to use each one

1) Lists: your flexible backpack

A list stores items in order and can be changed (mutable).

Create a list:

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

Get items by index (positions start at 0):

print(fruits[0])      # "apple"
print(fruits[2])      # "cherry"

Change an item:

fruits[1] = "blueberry"
print(fruits)         # ["apple", "blueberry", "cherry"]

Add items:

fruits.append("mango")        # add at the end
fruits.insert(1, "orange")    # add at a position
print(fruits)

Remove items:

fruits.remove("apple")  # remove by value (first match)
popped = fruits.pop()   # remove last and return it
print("Popped:", popped)
print(fruits)

Check length and membership:

print(len(fruits))          # how many items
print("mango" in fruits)    # True/False

Slice (get a part of the list):

numbers = [10, 20, 30, 40, 50]
print(numbers[1:4])   # [20, 30, 40]
print(numbers[-2:])   # last two: [40, 50]

Loop through a list:

for item in fruits:
    print(item)

2) Tuples: your sealed box

A tuple stores items in order but cannot be changed (immutable).

Create a tuple:

point = (3, 5)
print(point[0])   # 3
print(point[1])   # 5

Trying to change a tuple causes an error:

# point[0] = 7 # TypeError: 'tuple' object does not support item assignment

When are tuples useful?

Things that should not change: days of the week, fixed coordinates, RGB colors.
They can be a bit faster and safer because they don't change.

Unpacking tuples (handy trick):

x, y = point
print("x:", x, "y:", y)

3) Lists vs Tuples (quick compare)

List: [ ] brackets, can change (add/remove/modify).
Tuple: ( ) parentheses, cannot change after creation.
Use lists for collections that will change.
Use tuples for fixed data you want to keep safe.

4) Converting between them

Make a tuple from a list:

fruits = ["apple", "banana"]
fruits_t = tuple(fruits)
print(fruits_t)

Make a list from a tuple:

coords = (10, 20, 30)
coords_list = list(coords)
coords_list.append(40)
print(coords_list)

Mini exercise: List and Tuple challenge (5–8 minutes)

Make a list named backpack with items: "notebook", "pen", "snack".
Add "water bottle" to the end. Then insert "pencil" at position 1.
Remove "snack". Print the backpack and its length.
Make a tuple named start_pos with values (0, 0). Try to change start_pos[0] to 5. What happens?
Convert start_pos to a list, change the first value to 5, then convert it back to a tuple and print it.

Hints:

Use append, insert, remove, len
Use tuple() and list() to convert

Example solution (peek only after trying!):

backpack = ["notebook", "pen", "snack"]
backpack.append("water bottle")
backpack.insert(1, "pencil")
backpack.remove("snack")
print(backpack)
print("Items:", len(backpack))

start_pos = (0, 0)
# start_pos[0] = 5  # This would cause a TypeError

pos_list = list(start_pos)
pos_list[0] = 5
start_pos = tuple(pos_list)
print(start_pos)

Summary

Lists use [ ] and can change. Great for things that grow or shrink.
Tuples use ( ) and cannot change. Great for fixed, safe data.
You can access items by index, loop through them, slice parts, and convert between lists and tuples when needed.

You're now ready to organize data like a pro with lists and tuples!

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