Let's say you want to save a bunch of files somewhere, for instance in BLOBs. Let's say you want to dish these files out via a web page and have the client automatically open the correct application/viewer.
Assumption: The browser figures out which application/viewer to use by the mime-type (content-type?) header in the HTTP response.
Based on that assumption, in addition to the bytes of the file, you also want to save the MIME type.
How would you find the MIME type of a file? I'm currently on a Mac, but this should also work on Windows. 
Does the browser add this information when posting the file to the web page?
Is there a neat python library for finding this information? A WebService or (even better) a downloadable database?
There are 3 different libraries that wraps libmagic.
2 of them are available on pypi (so pip install will work):

filemagic
python-magic

And another, similar to python-magic is available directly in the latest libmagic sources, and it is the one you probably have in your linux distribution.
In Debian the package python-magic is about this one and it is used as toivotuo said and it is not obsoleted as Simon Zimmermann said (IMHO).
It seems to me another take (by the original author of libmagic).
Too bad is not available directly on pypi.
How to find the mime type of a file in python?