Python Lists — Full Notes

What Is a List?

Lists are created using square brackets and can store multiple items in a single variable.

Basic list creation:

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

Printing a List

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

Lists Allow Duplicate Values

Because lists are indexed, they can store the same value multiple times.

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

Changing List Items

Lists are mutable, so you can update, delete, or add items after creation.

1. Change a Single Item

Modify any list element using its index.

thislist = ["apple", "banana", "cherry"]
thislist[1] = "blackcurrant"
print(thislist)

2. Change a Range of Items

You can replace multiple values at once using slicing.

thislist = ["apple", "banana", "cherry", "orange", "kiwi", "mango"]
thislist[1:3] = ["blackcurrant", "watermelon"]
print(thislist)

Insert More Items Than Replaced

thislist = ["apple", "banana", "cherry"]
thislist[1:2] = ["blackcurrant", "watermelon"]
print(thislist)

Insert Fewer Items Than Replaced

thislist = ["apple", "banana", "cherry"]
thislist[1:3] = ["watermelon"]
print(thislist)

Insert Items

Use insert() to place an element at a specific index.

thislist = ["apple", "banana", "cherry"]
thislist.insert(2, "watermelon")
print(thislist)

Adding Items

append()

Adds an item at the end of the list.

thislist = ["apple", "banana", "cherry"]
thislist.append("orange")
print(thislist)

insert() at a Specific Position

thislist = ["apple", "banana", "cherry"]
thislist.insert(1, "orange")
print(thislist)

extend() from Another List

thislist = ["apple", "banana", "cherry"]
tropical = ["mango", "pineapple", "papaya"]
thislist.extend(tropical)
print(thislist)

extend() from Any Iterable

thislist = ["apple", "banana", "cherry"]
thistuple = ("kiwi", "orange")
thislist.extend(thistuple)
print(thislist)

Python List Methods

Python provides several built-in methods to work efficiently with lists.