Remove C and C++ comments using Python?

Question

I'm looking for Python code that removes C and C++ comments from a string. (Assume the string contains an entire C source file.)

I realize that I could .match() substrings with a Regex, but that doesn't solve nesting /*, or having a // inside a /* */.

Ideally, I would prefer a non-naive implementation that properly handles awkward cases.

Answer 1

This handles C++-style comments, C-style comments, strings and simple nesting thereof.

def comment_remover(text):
    def replacer(match):
        s = match.group(0)
        if s.startswith('/'):
            return " " # note: a space and not an empty string
        else:
            return s
    pattern = re.compile(
        r'//.*?$|/*.*?*/|'(?:\.|[^\'])*'|"(?:\.|[^"])*"',
        re.DOTALL | re.MULTILINE
    )
    return re.sub(pattern, replacer, text)

Strings needs to be included, because comment-markers inside them does not start a comment.

Edit: re.sub didn't take any flags, so had to compile the pattern first.

Edit2: Added character literals, since they could contain quotes that would otherwise be recognized as string delimiters.

Edit3: Fixed the case where a legal expression int/**/x=5; would become intx=5; which would not compile, by replacing the comment with a space rather then an empty string.