How to build a string by repeating a string with inserted values from an array

I'm trying to build a regular expression to search for alternative values populated from an array. I'm sure there is a shorthand way to achieve this.

searchValues = ['aa', 'bb', 'cc']
testValue    = "|(x)"

I'm looking for some magic using testValue where it is repeated with searchValues items replacing x, resulting in "(aa)|(bb)|(cc)".

You can use join on a comprehension to escape all values (in case they contain special characters) and form a pattern with interceding pipes:

import re 

searchValues = ['aa', 'bb', 'cc']
pattern = "|".join(re.escape(v) for v in searchValues)

# 'aa|bb|cc'

You don't actually need the parentheses but if you want them to form groups you can add then in the comprehension:

pattern = "|".join("("+re.escape(v)+")" for v in searchValues)

# '(aa)|(bb)|(cc)'

If you are certain that values don't contain special characters, a shorter expression can be used:

pattern = f"({')|('.join(searchValues)})"

If your values can potentially contain strings that happend to be a prefix of another value, you'll need to place the longer value before the shorter one. e.g. ['aab','aa','bb','cc'] instead of ['aa','bb','cc','aab',]. You can ensure that this is the case by sorting the searchValues on length: searchValues.sort(key=len,reverse=True)