python-regex-cheatsheet - quick reference for Python 2.7 regular expressions

Oct 13, 2026

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Concise cheat sheet for Python 2.7 regular expressions, summarizing core matching rules and common regex constructs. Covers literals vs special characters, anchors (^, $, \A, \Z), character classes ([], ranges, negation), alternation (R|S), and capture groups with precedence. Includes quantifiers ({m},{m,n},*,+,?) and special sequences for digits, whitespace, word boundaries, and non-word matches. Provides escaping guidance, backreferences via named/numbered groups (\g), extended regex syntax (lookahead/lookbehind, comments, conditionals, named groups), re.compile flags, and the primary re module functions with MatchObject/RegexObject methods.

LanguageEnglish

CategoryPresentations

FormatPDF

Pages1

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Python 2.7 Regular Expressions

Core matching rules and character classes

Quantifiers and special sequences

Escaping, backreferences, and extended syntax

re.compile flags and module-level functions

Python 2.7 Regular Expressions Non-special chars match themselves. Exceptions are special characters: \ Escape special char or start a sequence . . Match any char except newline, see re.DOTALL ^ Match start of the string, see re.MULTILINE $ Match end of the string, see re.MULTILINE [] Enclose a set of matchable chars R| S Match either regex R or regex S . () Create capture group, & indicate precedence After ' [', enclose a set, the only special chars are: ] End the set, if not the 1st char - A range, eg . a-c matches a, b or c ^ Negate the set only if it is the 1st char Quantifiers (append ' ?' for non-greedy): {m} Exactly m repetitions {m,n} From m (default 0) to n (default infinity) * 0 or more. Same as {,} + 1 or more. Same as {1,} ? 0 or 1. Same as {,1} Special sequences: \A Start of string \b Match empty string at word (\w+) boundary \B Match empty string not at word boundary \d Digit \D Non-digit \s Whitespace [ \t\n\r\f\v], see LOCALE,UNICODE \S Non-whitespace \w Alphanumeric: [0-9a-zA-Z_ ], see LOCALE \W Non-alphanumeric \Z End of string \g< id> Match prev named or numbered group,' < ' & ' > ' are literal, e .g . \g<0> or \g (not \g0 or \gname) Special character escapes are much like those already escaped in Python string literals. Hence regex ' \n' is same as regex ' \\n': \a ASCII Bell (BEL) \f ASCII Formfeed \n ASCII Linefeed \r ASCII Carriage return \t ASCII Tab \v ASCII Vertical tab \\ A single backslash \xHH Two digit hexadecimal character goes here \OOO Three digit octal char (or just use an initial zero, e.g . \0, \09)\DD Decimal number 1 to 99, match previous numbered group Extensions. Do not cause grouping, except 'P': (?iLmsux) Match empty string, sets re.X flags (?: . . . ) Non-capturing version of regular parens (?P . . . ) Create a named capturing group . (?P=name) Match whatever matched prev named group (?\# . . . ) A comment; ignored. (?= . . . ) Lookahead assertion, match without consuming (?! . . . ) Negative lookahead assertion (?<= . . . ) Lookbehind assertion, match if preceded (?< ! . . . ) Negative lookbehind assertion (?(id)y | n) Match 'y' if group 'id' matched, else 'n' Flags for re.compile(), etc. Combine with ' | ' : re.I == re.IGNORECASE Ignore case re.L == re.LOCALE Make \w, \b, and \s locale dependent re.M == re.MULTILINE Multiline re.S == re.DOTALL Dot matches all (including newline) re.U == re.UNICODE Make \w, \b, \d, and \s unicode dependent re.X == re.VERBOSE Verbose (unescaped whitespace in pattern is ignored, and '\#' marks comment lines) Module level functions: compile(pattern[, flags]) -> RegexObject match(pattern, string[, flags]) -> MatchObject search(pattner, string[, flags]) -> MatchObject findall(pattern, string[, flags]) -> list of strings finditer(pattern, string[, flags]) -> iter of MatchObjects split(pattern, string[, maxsplit, flags]) -> list of strings sub(pattern, repl, string[, count, flags]) -> string subn(pattern, repl, string[, count, flags]) -> (string, int) escape(string) -> string purge() \# the re cache RegexObjects (returned from compile()): .match(string[, pos, endpos]) -> MatchObject .search(string[, pos, endpos]) -> MatchObject .findall(string[, pos, endpos]) -> list of strings .finditer(string[, pos, endpos]) -> iter of MatchObjects .split(string[, maxsplit]) -> list of strings .sub(repl, string[, count]) -> string .subn(repl, string[, count]) -> (string, int) .flags \# int, Passed to compile() .groups \# int, Number of capturing groups .groupindex \# {}, Maps group names to ints .pattern \# string, Passed to compile() MatchObjects (returned from match() and search()): .expand(template) -> string, Backslash & group expansion .group([group1 . . . ]) -> string or tuple of strings, 1 per arg .groups([default]) -> tuple of all groups, non-matching=default .groupdict([default]) -> {}, Named gro

FAQs

How do I escape special characters in Python regular expressions?

Use a backslash to escape special characters, or start a sequence with \ to treat the next character appropriately. The cheat sheet notes that regex escapes behave similarly to Python string literal escapes.

What do ^, $, and re.MULTILINE change in matching behavior?

^ matches the start of the string, and $ matches the end of the string. With re.MULTILINE, these anchors apply in multiline contexts as specified in the sheet.

Which functions are available in the Python re module for finding matches?

The sheet lists compile, match, search, findall, finditer, split, sub, subn, and escape, along with methods on RegexObject such as .match, .search, .findall, and .finditer.

Oct 13, 2026

Upload by adawds