09 · Indexing & Slicing

Indexing and Slicing

This syntax is commonly used with:

Python starts counting from 0.

Copper

C  o  p  p  e  r
0  1  2  3  4  5

Positive Index

product = "Copper"

print(product[0])

Output:

C

Index 0 is the first item.

List Index

products = ["Copper", "Aluminum", "Nickel"]

print(products[1])

Output:

Aluminum

Negative Index

Negative indexes count from the end.

product = "Copper"

print(product[-1])

Output:

r

products[-1] returns the last list item.

Basic Slice

sequence[start:stop]

product = "Copper"

print(product[0:3])

Output:

Cop

The stop position is not included.

Omit Start / Omit Stop

product[:3]

product[3:]

List Slice

products = [
    "Copper",
    "Aluminum",
    "Nickel",
    "Zinc"
]

selected = products[1:3]

Result:

["Aluminum", "Nickel"]

Slice with Step

sequence[start:stop:step]

numbers = [0, 1, 2, 3, 4, 5, 6]

print(numbers[0:7:2])

Output:

[0, 2, 4, 6]

Reverse with [::-1]

text = "Copper"

reversed_text = text[::-1]

Result:

reppoC

products[::-1] returns the list in reverse order.