Regular Expression Cheat Sheet

Key Points

Intro to Regular Expressions	Regular expressions are a language for pattern matching.
Matching & Extracting	Regular expressions are useful for searching and cleaning data. Test regular expressions interactively with regex101.com or RegExr.com, and visualise them with regexper.com. Test yourself with RegexCrossword.com/ or via the quiz and exercises in this lesson.
Matching & Substitution	Regular expressions answers
Going further	There is a lot to regular expressions! It’s OK to use a cheat sheet.
Self-Multiple Choice Quiz	Regular expressions answers
More Exercises	Regular expressions answers

[] defines a range of characters.
. matches any character.
\ is used to escape the following character when that character is a special character. So, for example, a regular expression that found ‘.com’ would be \\.com because . is a special character that matches any character.
\d matches any single digit.
\w matches any part of word character (equivalent to [A-Za-z0-9]).
\s matches any space, tab, or newline.
^ asserts the position at the start of the line. So what you put after it will only match if they are the first characters of a line.
$ asserts the position at the end of the line. So what you put before it will only match if they are the last characters of a line.
\b adds a word boundary. Putting this either side of a stops the regular expression matching longer variants of words.
* matches the preceding element zero or more times. For example, ab*c matches ‘ac’, ‘abc’, ‘abbbc’, etc.
+ matches the preceding element one or more times. For example, ab+c matches ‘abc’, ‘abbbc’ but not ‘ac’.
? matches when the preceding character appears zero or one time.
{VALUE} matches the preceding character the number of times define by VALUE; ranges can be specified with the syntax {VALUE,VALUE}.
| means or.

Regular Expression Cheat Sheet (PDF) from qa-distiller.com. If you have access to a printer it would be useful to print this for reference during the workshop.
More detailed Regular Expression Cheat Sheet (PDF) by Dave Child from Regex page on cheatography.com. This cheat sheet has more detail than you will need in this workshop.

Online tools such as: Regxr, regex101, rexegper, myregexp, or whichever service you prefer.
Test yourself with RegexCrossword.com or via the quiz and exercises in this lesson.
You can visualize your regular expressions e.g. see [Oo]rgani.e visulaized on Regexper.com
Learn Regular Expressions with simple, interactive exercises at https://regexone.com/
Find a regex friend to consult when you need help.