| Special characters |
| \ |
escape special characters |
| . |
matches any character |
| ^ |
matches beginning of string |
| $ |
matches end of string |
| [5b-d] |
matches any chars '5', 'b', 'c' or 'd' |
| [^a-c6] |
matches any char except 'a', 'b', 'c' or '6' |
| R|S |
matches either regex R or regex S |
| () |
creates a capture group and indicates precedence |
| Quantifiers |
| * |
0 or more (append ? for non-greedy) |
| + |
1 or more (append ? for non-greedy) |
| ? |
0 or 1 (append ? for non-greedy) |
| {m} |
exactly mm occurrences |
| {m, n} |
from m to n. m defaults to 0, n to infinity |
| {m, n}? |
from m to n, as few as possible |
| Special sequences |
| \A |
start of string |
| \b |
matches empty string at word boundary (between \w and \W) |
| \B |
matches empty string not at word boundary |
| \d |
digit |
| \D |
non-digit |
| \s |
whitespace: [ \t\n\r\f\v] |
| \S |
non-whitespace |
| \w |
alphanumeric: [0-9a-zA-Z_] |
| \W |
non-alphanumeric |
| \Z |
end of string |
| \g<id> |
matches a previously defined group |
| Extensions |
| (?iLmsux) |
matches empty string, sets re.X flags |
| (?:...) |
non-capturing version of regular parentheses |
| (?P<name>...) |
creates a named capturing group |
| (?P=name) |
matches whatever matched previously named group |
| (?#...) |
a comment; ignored |
| (?=...) |
lookahead assertion: matches without consuming |
| (?!...) |
negative lookahead assertion |
| (?<=...) |
lookbehind assertion: matches if preceded |
| (?<!...) |
negative lookbehind assertion |
| (?(id)yes|no) |
match 'yes' if group 'id' matched, else 'no' |
