Programming
programming
text
patterns
What is Regular Expression (Regex)?
Definition
A regular expression (regex) is a pattern of characters that defines a search pattern. Regexes match, find, and replace text using special syntax — . matches any character, * means zero or more, and groups capture subpatterns.
Why It Matters
Regexes are used in input validation (emails, phone numbers), log parsing, search-and-replace, URL routing, and data extraction. Most programming languages and tools (grep, sed, editors) support regex natively. Mastering regex dramatically increases productivity.
Code Example
import re
pattern = r'\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z|a-z]{2,}\b'
email = '[email protected]'
print(bool(re.match(pattern, email))) # TrueLanguage: python
Frequently Asked Questions
What does the regex .* mean?
The dot . matches any single character (except newline by default). The asterisk * means zero or more of the preceding element. Together, .* matches any sequence of characters — it is the 'match everything' pattern.