Regular Expressions › Key Functions and Parameters

When working with regular expressions in Python, these are the essential functions and their most important parameters:

re.search(pattern, string, flags=0)

• pattern: The regex pattern to search for
• string: The text to search within
• flags: Optional modifiers like re.IGNORECASE, re.MULTILINE
• Returns: A match object for the first match, or None if no match

re.findall(pattern, string, flags=0)

• Returns all non-overlapping matches as a list of strings
• If the pattern has groups, returns a list of tuples containing the groups

re.finditer(pattern, string, flags=0)

• Returns an iterator of match objects for all matches
• Use when you need position information or access to groups

re.sub(pattern, repl, string, count=0, flags=0)

• repl: Replacement string or function
• count: Maximum number of replacements (0 means all)
• Backreferences like \1 can be used in the replacement string

re.split(pattern, string, maxsplit=0, flags=0)

• maxsplit: Maximum number of splits (0 means no limit)
• Returns a list of strings split at pattern matches

re.compile(pattern, flags=0)

• Pre-compiles a pattern for repeated use
• Returns a compiled pattern object with the same methods

Common Flags

• re.IGNORECASE (or re.I): Case-insensitive matching
• re.MULTILINE (or re.M): ^ and $ match at line boundaries
• re.DOTALL (or re.S): . matches newlines
• re.VERBOSE (or re.X): Allow comments and whitespace in patterns