How to use python-magic 5.19-1

Question

I need to determine MIME-types from files without suffix in python3 and I thought of python-magic as a fitting solution therefor. Unfortunately it does not work as described here: https://github.com/ahupp/python-magic/blob/master/README.md

What happens is this:

>>> import magic
>>> magic.from_file("testdata/test.pdf")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'module' object has no attribute 'from_file'

So I had a look at the object, which provides me with the class Magic for which I found documentation here: http://filemagic.readthedocs.org/en/latest/guide.html

I was surprised, that this did not work either:

>>> with magic.Magic() as m:
...     pass
... 
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: __init__() missing 1 required positional argument: 'ms'
>>> m = magic.Magic()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: __init__() missing 1 required positional argument: 'ms'
>>> 

I could not find any information about how to use the class Magic anywhere, so I went on doing trial and error, until I figured out, that it accepts instances of LP_magic_set only for ms. Some of them are returned by the module's methods magic.magic_set() and magic_t(). So I tried to instanciate Magic with either of them. When I then call the file() method from the instance, it will always return an empty result and the errlvl() method tells me error no. 22. So how do I use magic anyway?

Answer 1

I think that you are confusing different implementations of "python-magic"

You appear to have installed python-magic-5.19.1, however, you reference firstly the documentation for python-magic-0.4.6, and secondly filemagic-1.6. I think that you are better off using python-magic-0.4.6 as it is readily available at PYPI and easily installed via pip into virtualenv environments.

Documentation for python-magic-5.19.1 is hard to come by, but I managed to get it to work like this:

>>> import magic
>>> m=magic.open(magic.MAGIC_NONE)
>>> m.load()
0
>>> m.file('/etc/passwd')
'ASCII text'
>>> m.file('/usr/share/cups/data/default.pdf')
'PDF document, version 1.5'

You can also get different magic descriptions, e.g. MIME type:

>>> m=magic.open(magic.MAGIC_MIME)
>>> m.load()
0
>>> m.file('/etc/passwd')
'text/plain; charset=us-ascii'
>>> m.file('/usr/share/cups/data/default.pdf')
'application/pdf; charset=binary'

or for more recent versions of python-magic-5.30

>>> import magic
>>> magic.detect_from_filename('/etc/passwd')
FileMagic(mime_type='text/plain', encoding='us-ascii', name='ASCII text')
>>> magic.detect_from_filename('/etc/passwd').mime_type
'text/plain'