What would be the most conservative way to check if a file-name is valid in Python on all platforms (including mobile platforms like Android, iOS)?
Ex.
this_is_valid_name.jpg -> Valid
**adad.jpg -> Invalid
a/ad -> Invalid
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possible duplicate of [Check whether a path is valid in Python without creating a file at the path's target](http://stackoverflow.com/questions/9532499/check-whether-a-path-is-valid-in-python-without-creating-a-file-at-the-paths-ta) – isedev Mar 13 '14 at 21:16
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That one is about file path. If accessible or not. I am concerned with the most general file naming convention across OSes. – gat Mar 13 '14 at 21:17
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`**adad.jpg` is a valid name e.g. in GNU/Linux: `open('**adad.jpg', 'w')` will create it. – bereal Mar 13 '14 at 21:18
1 Answers
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The most harsh way to check if a file would be a valid filename on you target OSes is to check it against a list of properly tested filenames.
valid = myfilename in ['this_is_valid_name.jpg']
Expanding on that, you could define a set of characters that you know are allowed in filenames on every platform :
valid = set(valid_char_sequence).issuperset(myfilename)
But this is not going to be enough, as some OSes have reserved filenames.
You need to either exclude reserved names or create an expression (regexp) matching the OS allowed filename domain, and test your filename against that, for each target platform.
AFAIK, Python does not offer such helpers, because it's Easier to Ask Forgiveness than Permission. There's a lot of different possible combinations of OSes/filesystems, it's easier to react appropriately when the os raises an exception than to check for a safe filename domain for all of them.
