Help:Regular expressions

A regular expression (regex) is a sequence of characters defining a search pattern. On the wiki, they are commonly used for finding and replacing text through Special:ReplaceText (staff only), AutoWikiBrowser, Pywikibot, or Scribunto/Lua modules.

Each tool/programming language uses its own ruleset for regular expressions:

• Special:ReplaceText supports a small subset (( ) . * + ? [ ]) of the PHP and MySQL/PostgreSQL regular-expression set.
• AutoWikiBrowser uses .NET regular expressions.
• Pywikibot uses Python regular expressions.
• Lua/Scribunto pattern are similar to regular expressions, but not identical. See this page for a list of differences.

If you need help with regular expressions, you may post on the talk page, or join the Nookipedia Discord and ask in the #wiki-tech channel.

Testing

There are several online tools to test our patterns. A small selection is listed below.

• regex101.com
• regexr.com
• extendsclass.com

Examples

Below is a list of examples of regular expressions that may help you on the wiki. Feel free to expand this list.

• Replacing instances of {{I|Item Name}} with {{I|Item Name|New Horizons}} (Python):

Find: {{I\|(?!.*\|)(.*?)}}

Replace: {{I|\1|New Horizons}}

• Matching a multi-line Foreignname template and adding a new "See also" section after it (Python):

Find: {{Foreignname([\s\S]*?\n}})

Replace: {{Foreignname\1\n\n==See also==

• Add f#-img parameters after each furn# parameter in instances of house templates; the template takes in the furniture name as a parameter and returns a filename (AWB):

Find: \|furn([1-9]\d?)= (.*)

Replace: |furn$1= $2\n|f$1-img= {{subst:Example|$2}}

• Prepend an html selector to every CSS property in a stylesheet (source on StackOverflow by Ryan Worth):

Find: (^(?:\s|[^@{])*?|[},]\s*)(\/\/.*\s+|.*\/\*[^*]*\*\/\s*|@media.*{\s*|@font-face.*{\s*)*([.#]?-?[_a-zA-Z]+[_a-zA-Z0-9-]*)(?=[^}]*{)

Replace: $1$2html $3

• Move width attributes into existing style attribute (PHP):

Find:  width="(.*)\%"(.*)style="

Replace: $2style="width: $1%; 

Notes: Note the space at the start of the find and the end of the replace. May mess up if multiple elements are on the same line.