To write these tempfiles, Django uses the tempfile module in python. You can see django's code in django/core/files/temp.py
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A django temp file is a tempfile.NamedTemporaryFile
. Here's a link to the code. The default settings in that constructor (plus code that's in django) calls for the file to be deleted when it is closed.
So watch out for filehandle links; if they're not getting deleted, it is likely that your code is leaking the filehandle, and never closing it.