Regular Expressions

A pattern language for text. Python's re module:

Three workhorses

• re.findall(pattern, text) — every non-overlapping match, as a list
• re.search(pattern, text) — first match anywhere, or None
• re.sub(pattern, repl, text) — replace matches

Cheat sheet

• \d digit · \w word char · \s whitespace
• + one or more · * zero or more · ? optional
• ( ) capture group · [abc] any of a/b/c

Use raw strings

Always prefix patterns with r to avoid backslash hell: r"\d+".

Try it

1. Extract all numbers from "order #1234, total ₹5,600".
2. Replace double-spaces with single in "a b c".