Python Lists

What Is A List?

A list stores multiple values in one variable. Lists are useful when values belong together, such as scores, names, prices, or tasks.

scores = [80, 75, 92]
names = ["Asha", "Riya", "Kabir"]

List items can be accessed, changed, added, and removed.

Indexing Lists

Python list indexes start at 0.

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

print(fruits[0])
print(fruits[2])

Output:

apple
mango

Negative indexes count from the end.

print(fruits[-1])

This prints mango.

Updating Items

Lists are mutable, which means you can change their contents.

fruits = ["apple", "banana", "mango"]
fruits[1] = "orange"

print(fruits)

Output:

['apple', 'orange', 'mango']

Adding And Removing Items

Use append() to add an item at the end.

tasks = ["read", "practice"]
tasks.append("review")

Use pop() to remove and return an item by index. Without an index, it removes the last item.

last_task = tasks.pop()

Use remove() when you want to remove by value.

tasks.remove("read")

Looping Through A List

You can use a for loop to process every item.

scores = [80, 75, 92]

for score in scores:
    print(score)

To count items, use len().

print(len(scores))

List Slices

Slicing creates part of a list.

numbers = [10, 20, 30, 40]
print(numbers[1:3])

Output:

[20, 30]

The slice starts at index 1 and stops before index 3.

Common Mistakes

A common mistake is using an index that is too large.

items = ["pen", "book"]
print(items[2])

The valid indexes are 0 and 1, so this raises an IndexError.

Another mistake is mixing up append() and remove(). append() adds a value. remove() deletes the first matching value and raises an error if the value is not found.

Quick Summary

• A list stores multiple values.
• List indexes start at 0.
• Lists are mutable, so items can be changed.
• Use append() to add, pop() to remove by index, and remove() to remove by value.
• Use len() to count items.
• Use a for loop to process list items.

Practice Quiz

Now practice this topic with MCQs and explanations:

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