What is Regex?

• Regular Expressions
• a way to specify part of a string that matches something
• a way to check if a string contains something

Why Regex?

• More versatile
• Universal - available in Tableau & Alteryx
• It is used for finding, removing or replacing parts of string.
• \w{3} - 3 word like characters - My cat is called Bob (matches to every 3 letters next to each other - ‘cat’, ‘cal’, ’led’, ’Bob’
• String processing

How to work well with Regex?

• Be vague enough to capture everything you want
• Build up expressions for trial and testing

Quantifiers - how many of something?

Special Characters:

.[]{}()\*+?|^$

Character Classes:

. = everything!

\w = character

\d = digit

\s = whitespace

Formula:

REGEX_CountMatches(String, Pattern)

How many times in this string does this pattern show up? Output is a number

REGEX_Replace(String, Pattern, Replace)

Output is the String with replacement In this string, find this pattern and replace it with this string

REGEX_Match(String, Pattern)

Does this string contain this pattern? Output is -1 or 0 (True or False)

Examples:

"My cat is called Bob and born 10th May. I have Many cats." - For reference

1. “.” - Every separate character
2. “.*” - Sentence as a whole
3. “.+” - Sentence as a whole - one or more
4. “\w” = alphanumeric and ‘_’ - every character that isnt whitespace
5. “\w+” - each word - greedy
6. “\w{3}” = 3 alphanumerics - 3 word like characters - My cat is called Bob (matches to every 3 letters next to each other - ‘cat’, ‘cal’, ’led’, ’Bob’
7. “B\w+” - words beginning with B
8. “[A-Z]\w+” - includes a list - will look for those characters in a string - [A-Z] words beginning with a capital letter
9. “[A-Z]*\w+” - words beginning with 0 or more capitals
10. “^\w+” = start of a string
11. “\w+$” - end of the string
12. “My” - the word “My”
13. “M.y” - M followed by any character followed by y - only 1 character - word, blank, word
14. “M..y” M followed by any character followed by y - only 2 character - word, blank, blank, word
15. “M.+y” - will detect all y’s (greedy) until the last y. Sentence as a whole - M, 1 or more blanks, y (greedy)
16. “M.+?y” - ‘?’ makes it not greedy - M, blank y, - Stops at ‘May’
17. “M\w*y” - M, 0 or more alphanumerics, y (greedy) - My, May, Many
18. ( ) - Group Greedy
19. “\s” - whitespace - one character - matches with all the whitespace
20. “\d” - digit - 0-9
21. “\d{2}” - works for double digit number
22. “\u” - uppercase letter
23. “\u\u?\d\u?\s\d\u\u - ‘?’ - makes it optional - e.g. Postcodes (because its unique)
24. “\n” - New Line
25. “.+” - one or more of anything (any character)
26. \S - NOT space
27. [^s] - not an S