Question

Having a bit of trouble coming up with a regex statement for the following room numbers:

C001B --> C1B //remove "leading" zeros after first set of letters
C100B --> C100B
CB001B --> CB1B //remove "leading" zeros after first set of letters
001B --> 1B //remove leading zeros

Essentially, remove all zeros which is not preceded by a numeral?

Answer 1

Well, to match such zeros you could use a negative lookbehind, such as (?<![^a-zA-Z]), to ensure that the matched area is not preceded by anything but a letter. By inserting this before your match, it will ensure that whatever comes immediately before doesn’t match the pattern contained, here [^a-zA-Z], which also counts for matches at the very beginning of a line.

re.sub("(?<![^a-zA-Z])0+","",number)