advancedAdvanced Topics

Regular Expressions

Pattern matching with the re module.

In this lesson

01Basic Pattern Matching
02Groups and Matching

01Basic Pattern Matching

Use the re module for powerful string pattern matching.

Python

1import re
2
3text = "Contact: alice@example.com or bob@test.org"
4
5# Find all emails
6emails = re.findall(r'[\w.]+@[\w.]+', text)
7print(emails)
8
9# Search and replace
10cleaned = re.sub(r'\d+', 'NUM', "I have 3 cats and 12 dogs")
11print(cleaned)

Output

['alice@example.com', 'bob@test.org']
I have NUM cats and NUM dogs

02Groups and Matching

Extract parts of matches using groups.

Python

1import re
2
3pattern = r'(\d{4})-(\d{2})-(\d{2})'
4text = "Today is 2026-06-08 and tomorrow is 2026-06-09"
5
6match = re.search(pattern, text)
7if match:
8    print(f"Full: {match.group(0)}")
9    print(f"Year: {match.group(1)}")
10    print(f"Month: {match.group(2)}")
11    print(f"Day: {match.group(3)}")

Output

Full: 2026-06-08
Year: 2026
Month: 06
Day: 08

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