Regular Expressions in Python

Regular expressions (regex) are powerful patterns for matching and manipulating text. They're used for validation (emails, phone numbers), searching, extracting data, and cleaning text.

Python's re module provides full regex support. Patterns can look complex at first, but they're built from simple building blocks.

We'll start with basics and build up with lots of examples.

Importing re and Basic Patterns

Import re and use raw strings (r"") for patterns to avoid escape issues.

Common characters:

• . – any character (except newline)
• ^ – start of string
• $ – end of string
• * – 0 or more
• + – 1 or more
• ? – 0 or 1
• \d – digit
• \w – word character
• \s – whitespace

Main re Methods

search() – first match anywhere match() – match at start findall() – all matches as list sub() – replace matches

Groups and Capturing

Use () to capture parts of the match.

Flags for Advanced Matching

re.IGNORECASE, re.MULTILINE, re.DOTALL etc.

Practical Examples

Validate simple email:

Extract phone numbers:

Quick Quiz