Is it a function?

Sometimes you want to know whether something is a function or not. The obvious solution is to check the object class with isinstance. The class of functions is function, but you can't access it directly. You can instead get type of any existing function:

FunctionType = type(lambda: None)

Now you can do checking:

def isfunction(object):
    return isinstance(object, FunctionType)

Luckily all above code is already written for you: FunctionType is an existing member of types and isfunction already exists in the inspect module.

Note, that you usually don't care whether something is a function, but rather if it's callable or not. It can be done with callable:

>>> callable(int)
True
>>> callable(42)
False
>>> callable(callable)
True