Character Classes Fundamentals

Square Bracket Notation

In regular expressions, a character class (or set) allows you to tell the regex engine to match only one out of several characters. This is done by placing the characters inside square brackets [].

Basic Usage

If you want to match the word "grey" or "gray", you can use gr[ea]y. This tells Python to match 'g', 'r', then either 'e' or 'a', and finally 'y'.

Character Ranges

Listing every character you want to match can be tedious. You can use a hyphen - to define a range of characters.

• [0-9]: Matches any single digit from 0 to 9.
• [a-z]: Matches any lowercase letter from a to z.
• [A-Z]: Matches any uppercase letter from A to Z.
• [A-Za-z]: Matches any letter (uppercase or lowercase).