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Regular Expressions Cheat Sheet

  • [] 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 one or zero times
  • {VALUE} matches the preceding character the number of times define by VALUE; ranges can be specified with the syntax {VALUE,VALUE}
  • | means or
  • Check your regex with: regex101 https://regex101.com/, rexegper http://regexper.com/, or myregexp http://myregexp.com/
  • Test yourself with: Regex Crossword https://regexcrossword.com/ or our The Multiple Choice Quiz http://data-lessons.github.io/library-data-intro/05-quiz/