Index

Definition

An index is a numerical representation used to access elements within an ordered collection, such as a list or string. In Python, indices start at 0 and can be positive or negative.

5 Must Know Facts For Your Next Test

1. Indices in Python start at 0, meaning the first element of a list has an index of 0.
2. Negative indices count from the end of the list, with -1 being the last element.
3. Using an out-of-range index will raise an IndexError exception.
4. Slicing can create sublists by specifying start and end indices.
5. The len() function returns the number of items in a list, which helps prevent IndexError.

Review Questions

• What is the index of the first element in a Python list?
• How do negative indices work in Python?
• What error occurs if you try to access an out-of-range index?

Related terms

List: An ordered collection of elements that can be indexed and sliced.

String: A sequence of characters that can be indexed like a list.

Slicing: The process of retrieving a subset of elements from an ordered collection using start and end indices.