Create (sane/safe) filename from any (unsafe) string

Question

I want to create a sane/safe filename (i.e. somewhat readable, no \"strange\" characters, etc.) from some random Unicode string (mich might contain just anything).

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Answer 1

There are a few reasonable answers here, but in my case I want to take something which is a string which might have spaces and punctuation and rather than just removing those, i would rather replace it with an underscore. Even though spaces are an allowable filename character in most OS's they are problematic. Also, in my case if the original string contained a period I didn't want that to pass through into the filename, or it would generate "extra extensions" that I might not want (I'm appending the extension myself)

def make_safe_filename(s):
    def safe_char(c):
        if c.isalnum():
            return c
        else:
            return "_"
    return "".join(safe_char(c) for c in s).rstrip("_")

print(make_safe_filename( "hello you crazy $#^#& 2579 people!!! : die!!!" ) + ".gif")

prints:

hello_you_crazy_______2579_people______die___.gif