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

Here is what I came with, being inspired by uglycoyote:

import time

def make_safe_filename(s):
    def safe_char(c):
        if c.isalnum() or c=='.':
            return c
        else:
            return "_"

    safe = ""
    last_safe=False
    for c in s:
      if len(safe) > 200:
        return safe + "_" + str(time.time_ns() // 1000000)

      safe_c = safe_char(c)
      curr_safe = c != safe_c
      if not last_safe or not curr_safe:
        safe += safe_c
      last_safe=curr_safe
    return safe

And to test:

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