You’ll be able to
- Match patterns with
re.search,re.match,re.findall - Use character classes, quantifiers, and anchors
- Capture groups to extract substrings
- Substitute matched text with
re.sub
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Why this matters
re powers log parsing, Django URL routing, and every scraper. Catastrophic backtracking in nested quantifiers has taken down real services (Cloudflare 2019). Knowing re.compile, named groups, and re.VERBOSE separates hobbyists from engineers.
Common pitfalls
- Recompiling the same pattern in a loop — hoist to module scope with
re.compile()for a real speedup. - Using greedy
.*when you want.*?— you'll match across delimiters and get one giant blob. - Parsing HTML or emails with regex — reach for
BeautifulSouporemail.parserbefore you regret it.