Introduction

Regular expressions (regex) are powerful tools for pattern matching and text manipulation. Python’s built-in re module provides full regex support. This cheat sheet covers all major patterns and functions you’ll need.

Basic Pattern Matching

import re

# Search for a pattern

result = re.search(r’\d+’, ‘Order 1234 shipped’)

if result:

    print(result.group())  # 1234

# Find all matches

result = re.findall(r’\d+’, ‘Call 555-1234 or 555-5678’)

print(result)  # [‘555’, ‘1234’, ‘555’, ‘5678’]

Common Regex Patterns

# Email validation

email_pattern = r’^[\w.-]+@[\w.-]+\.\w{2,}$’

print(bool(re.match(email_pattern, ‘user@example.com’)))  # True

# Phone number

phone = r’\(?\d{3}\)?[-.\s]?\d{3}[-.\s]?\d{4}’

print(re.findall(phone, ‘Call 555-123-4567 now’))  # [‘555-123-4567’]

# URL

url_pattern = r’https?://[\w./%-]+’

Substitution with re.sub

import re

# Remove all digits

clean = re.sub(r’\d’, ”, ‘abc123def456’)

print(clean)  # abcdef

# Replace spaces with underscores

slug = re.sub(r’\s+’, ‘_’, ‘Hello World Foo’)

print(slug)  # Hello_World_Foo

Groups and Capture

# Extract groups

match = re.search(r'(\d{4})-(\d{2})-(\d{2})’, ‘2024-01-15’)

if match:

    year, month, day = match.groups()

    print(year, month, day)  # 2024 01 15

Conclusion

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