[ACCEPTED]-How to test if a class attribute is an instance method-instance

Accepted answer

Score: 20

def hasmethod(obj, name):
    return hasattr(obj, name) and type(getattr(obj, name)) == types.MethodType

Score: 8

You can use the inspect module:

class A(object):
    def method_name(self):
        pass


import inspect

print inspect.ismethod(getattr(A, 'method_name')) # prints True
a = A()
print inspect.ismethod(getattr(a, 'method_name')) # prints True

Score: 7

import types

print isinstance(getattr(your_object, "your_attribute"), types.MethodType)

Score: 5

This function checks if the attribute exists 2 and then checks if the attribute is a method 1 using the inspect module.

import inspect

def ismethod(obj, name):
    if hasattr(obj, name):
        if inspect.ismethod(getattr(obj, name)):
            return True
    return False

class Foo:
    x = 0
    def bar(self):
        pass

foo = Foo()
print ismethod(foo, "spam")
print ismethod(foo, "x")
print ismethod(foo, "bar")

Score: 1

Be aware that @classmethod-decorated functions will 14 pass all the tests in other answers. Do 13 you want these to be considered 'instance 12 methods'? Maybe it's just semantics, but 11 they by definition operate on the class, not 10 the spawned instance. I am not sure about 9 the cases where hasmethod2 (my proposed 8 solution) fails, but at least it can be 7 wary of class methods:


import inspect
import types

def hasmethod(obj, name):
    return hasattr(obj, name) and type(getattr(obj, name)) == types.MethodType

def hasmethod2(obj, name):
    try:
        attr = getattr(obj, name)
        return not inspect.isclass(attr.__self__)
    except AttributeError:
        return False

class Test(object):
    testdata = 123

    def testmethod(self):
        pass

    @classmethod
    def testmethod2(cls):
        pass

# Returns True. This may be undesired depending on your definition of 'instance method'
hasmethod(Test(), 'testmethod2')
 
# Returns False
hasmethod2(Test(), 'testmethod2')

It works because __self__ is 6 bound to the primary calling argument (class 5 instance for classmethod, object instance 4 for normal attributes, module or nothing 3 for various built-ins). Thus, checking for 2 the existence of __self__ and that __self__ is not a class 1 rules out non-function attributes and classmethods, respectively.

Source: stackoverflow.com

[ACCEPTED]-How to test if a class attribute is an instance method-instance

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