Python: Check if uploaded file is jpg

Question

How can I check if a file uploaded by a user is a real jpg file in Python (Google App Engine)?

This is how far I got by now:

Script receives image via HTML F

Answer 1

A more general solution is to use the Python binding to the Unix "file" command. For this, install the package python-magic. Example:

import magic

ms = magic.open(magic.MAGIC_NONE)
ms.load()
type =  ms.file("/path/to/some/file")
print type

f = file("/path/to/some/file", "r")
buffer = f.read(4096)
f.close()

type = ms.buffer(buffer)
print type

ms.close()