Stripping everything but alphanumeric chars from a string in Python

Question

What is the best way to strip all non alphanumeric characters from a string, using Python?

The solutions presented in the PHP variant of this question will probably

Answer 1

How about:

def ExtractAlphanumeric(InputString):
    from string import ascii_letters, digits
    return "".join([ch for ch in InputString if ch in (ascii_letters + digits)])

This works by using list comprehension to produce a list of the characters in InputString if they are present in the combined ascii_letters and digits strings. It then joins the list together into a string.