python 3: how to check if an object is a function?

Question

Am I correct assuming that all functions (built-in or user-defined) belong to the same class, but that class doesn't seem to be bound to any variable by default?

How can I check that an object is a function?

I can do this I guess:

def is_function(x):
  def tmp()
    pass
  return type(x) is type(tmp)

It doesn't seem neat, and I'm not even 100% sure it's perfectly correct.

Solution 1

in python2:

callable(fn)

in python3:

isinstance(fn, collections.Callable)

as Callable is an Abstract Base Class, this is equivalent to:

hasattr(fn, '__call__')

Solution 2

How can I check that an object is a function?

Isn't this same as checking for callables

hasattr(object, '__call__')

and also in python 2.x

callable(object) == True

Solution 3

You can do:

def is_function(x):
    import types
    return isinstance(x, types.FunctionType) \
        or isinstance(x, types.BuiltinFunctionType)