Python 3.3.2 check that object is of type file

Question

I'm porting from Python 2.7 to Python 3.3.2. In Python 2.7, I used to be able to do something like assert(type(something) == file), but it seems that in Python 3.3.2 this is wrong. How do I do a similar thing in Python 3.3.2?

Answer 1

Python 3 file objects are part of the io module, test against ABC classes in that module:

from io import IOBase

if isinstance(someobj, IOBase):

Don't use type(obj) == file in Python 2; you'd use isinstance(obj, file) instead. Even then, you would want to test for the capabilities; something the io ABCs let you do; the isinstance() function will return True for any object that implements all the methods the Abstract Base Class defines.

Demo:

>>> from io import IOBase
>>> fh = open('/tmp/demo', 'w')
>>> isinstance(fh, IOBase)
True
>>> isinstance(object(), IOBase)
False