CamelCase -> camel_case

camel2underscore.py

import re

_endpiecere = re.compile(r"[A-Z]+$")
_camelre = re.compile(r"([A-Z]+)(?=[0-9a-z])")

def camel2underscore(camel):
    camel = _endpiecere.sub(lambda m: "_" + m.group(0).lower(), camel)
    def insert(match):
        m = match.group(0).lower()
        return "_" + (m if len(m) == 1 else m[:-1] + "_" + m[-1])
    return _camelre.sub(insert, camel).lstrip("_")

if __name__ == "__main__":
    def passert(a, b):
        if a == b:
            print "ok:", a
        else:
            print "FAIL:", a, "!=", b

    passert(camel2underscore("SimpleCase"), "simple_case")
    passert(camel2underscore("LuckyNumberS7evin"), "lucky_number_s7evin")
    passert(camel2underscore("LLVMContext"), "llvm_context")
    passert(camel2underscore("MarkAndSweepGC"), "mark_and_sweep_gc")