Regex Cheat Sheet

Regex Syntax

Characters
Character Matches
a a character
. Any character (except newline)
\. . character
\\ \ character
\* * character
Character Classes
  Matches Description
[abcd] Any one of the letters a through d Set of characters
[^abcd] Any character but a, b, c, or d Complement of a set of characters
[a-d] Any one of the letters a through d Range of characters
[a-dz] Any of a, b, c, d, or z Range of characters
Special Sequences
Type Expression Equivalent To Description
Word Character \w [a-zA-Z0-9_] Alphanumeric or underscore
Non-word Character \W [^a-zA-Z0-9_] Anything but a word character
Digit Character \d [0-9] Numeric
Non-digit Character \D [^0-9] Non-numeric
Whitespace Character \s [ \t\n\r\f\v] Whitespace
Non-whitespace Character \S [^ \t\n\r\f\v] Anything but a whitespace character
Anchors
Anchor Matches
^ Start of the string
$ End of the string
\b Boundary between word and non-word characters
Groups
Group Type Expression
Capturing ( ... )
Non-capturing (?: ... )
Quantifiers/Repetition
Quantifier Modification
{5} Match expression exactly 5 times
{2,5} Match expression 2 to 5 times
{2,} Match expression 2 or more times
{,5} Match expression 0 to 5 times
* Match expression 0 or more times
{,} Match expression 0 or more times
? Match expression 0 or 1 times
{0,1} Match expression 0 or 1 times
+ Match expression 1 or more times
{1,} Match expression 1 or more times
Non-greedy quantifiers
Quantifier Modification
{2,5}? Match 2 to 5 times (less preferred)
{2,}? Match 2 or more times (less preferred)
{,5}? Match 0 to 5 times (less preferred)
*? Match 0 or more times (less preferred)
{,}? Match 0 or more times (less preferred)
?? Match 0 or 1 times (less preferred)
{0,1}? Match 0 or 1 times (less preferred)
+? Match 1 or more times (less preferred)
{1,}? Match 1 or more times (less preferred)
Alternators
Quantifier Modification
ABC|DEF Match string ABC or string DEF
Lookaround
Quantifier Modification
(?=abc) Zero-width match confirming abc will match upcoming chars
(?!abc) Zero-width match confirming abc will not match upcoming chars

Python

functions
Function Purpose Usage
re.search Return a match object if pattern found in string re.search(r'[pat]tern', 'string')
re.finditer Return an iterable of match objects (one for each match) re.finditer(r'[pat]tern', 'string')
re.findall Return a list of all matched strings (different when capture groups) re.findall(r'[pat]tern', 'string')
re.split Split string by regex delimeter & return string list re.split(r'[ -]', 'st-ri ng')
re.compile Compile a regular expression pattern for later use re.compile(r'[pat]tern')
flags
Flag Description
re.IGNORECASE Match uppercase and lowercase characters interchangeably
re.VERBOSE Ignore whitespace characters and allow # comments
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