A journal of habit-forming shenanigans
The re module offers a set of functions that allows us to search a string for a match:
| Function | Description |
|---|---|
| findall | Returns a list containing all matches |
| search | Returns a Match object if there is a match anywhere in the string |
| split | Returns a list where the string has been split at each match |
| sub | Replaces one or many matches with a string |
Metacharacters are characters with a special meaning:
| Character | Description | Example |
|---|---|---|
| [] | Matches a set of characters in the listed set | "[a-m]" |
| \ | Signals a special sequence (can also be used to escape special characters) | "\d" |
| . | Any character (except newline character) | "he..o" |
| ^ | Starts with | "^hello" |
| $ | Ends with | "world$" |
| * | Zero or more occurrences | "aix*" |
| *? | Zero or more occurrences (non-greedy) | "aix*?" |
| + | One or more occurrences | "aix+" |
| +? | One or more occurrences (non-greedy) | "aix+?" |
| {} | Exactly the specified number of occurrences | "al{2}" |
| | | Either or | "falls|stays" |
| () | Capture and group |
A special sequence is a \\ followed by one of the characters in the list below, and has a special meaning:
| Character | Description | Example |
|---|---|---|
| \A | Returns a match if the specified characters are at the beginning of the string | "\AThe" |
| \b | Returns a match where the specified characters are at the beginning or at the end of a word | r"\bain" r"ain\b" |
| \B | Returns a match where the specified characters are present, but NOT at the beginning (or at the end) of a word | r"\Bain" r"ain\B" |
| \d | Returns a match where the string contains digits (numbers from 0-9) | "\d" |
| \D | Returns a match where the string DOES NOT contain digits | "\D" |
| \s | Returns a match where the string contains a white space character | "\s" |
| \S | Returns a match where the string DOES NOT contain a white space character | "\S" |
| \w | Returns a match where the string contains any word characters (characters from a to Z, digits from 0-9, and the underscore _ character) | "\w" |
| \W | Returns a match where the string DOES NOT contain any word characters | "\W" |
| \Z | Returns a match if the specified characters are at the end of the string | "Spain\Z" |
A set is a set of characters inside a pair of square brackets [] with a special meaning:
| Set | Description |
|---|---|
| [arn] | Returns a match where one of the specified characters (a, r, or n) are present |
| [a-n] | Returns a match for any lower case character, alphabetically between a and n |
| [^arn] | Returns a match for any character EXCEPT a, r, and n |
| [0123] | Returns a match where any of the specified digits (0, 1, 2, or 3) are present |
| [0-9] | Returns a match for any digit between 0 and 9 |
| [0-5][0-9] | Returns a match for any two-digit numbers from 00 and 59 |
| [a-zA-Z] | Returns a match for any character alphabetically between a and z, lower case OR upper case |
| [+] | In sets, +, *, ., |, (), $,{} has no special meaning, so [+] means: return a match for any + character in the string |