How to check whether a variable is a class or not?


Question

I was wondering how to check whether a variable is a class (not an instance!) or not.

I've tried to use the function isinstance(object, class_or_type_or_tuple) to do this, but I don't know what type would a class will have.

For example, in the following code

class Foo: pass  
isinstance(Foo, **???**) # i want to make this return True.

I tried to substitute "class" with ???, but I realized that class is a keyword in python.

1
207
4/24/2016 5:39:53 PM

Accepted Answer

Even better: use the inspect.isclass function.

>>> import inspect
>>> class X(object):
...     pass
... 
>>> inspect.isclass(X)
True

>>> x = X()
>>> isinstance(x, X)
True
>>> y = 25
>>> isinstance(y, X)
False
286
4/16/2016 11:23:47 PM

The inspect.isclass is probably the best solution, and it's really easy to see how it's actually implemented

def isclass(object):
    """Return true if the object is a class.

    Class objects provide these attributes:
        __doc__         documentation string
        __module__      name of module in which this class was defined"""
    return isinstance(object, (type, types.ClassType))

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