I don't think I understand your question (nor am I an expert on Python regex!)...but just to be clear, Python's regular expression standard library is named `re

I don't think I understand your question (nor am I an expert on Python regex!)...but just to be clear, Python's regular expression standard library is named `re`. But there is an external lib – ostensibly a drop-in replacement – that goes by the name of `regex`. It is the `regex` library that supports variable lookbehind, not Python's standard library `re` https://pypi.org/project/regex/ https://pypi.org/project/regex/