How to tell if a file is gzip compressed?

Question

I have a Python program which is going to take text files as input. However, some of these files may be gzip compressed.

Is there a cross-platform, usable from Py

Answer 1

Doesn’t seem to work well in python3...

import mimetypes
filename = "./datasets/test"

def file_type(filename):
    type = mimetypes.guess_type(filename)
    return type
print(file_type(filename))

returns (None, None) But from the unix command "File"

:~> file datasets/test datasets/test: gzip compressed data, was "iostat_collection", from Unix, last modified: Thu Jan 29 07:09:34 2015