In python it's possible to use '.' in order to access object's dictionary items. For example:
class test( object ) :
def __init__( self ) :
self.b = 1
def foo( self ) :
pass
obj = test()
a = obj.foo
From above example, having 'a' object, is it possible to get from it reference to 'obj' that is a parent namespace for 'foo' method assigned? For example, to change obj.b into 2?
On bound methods, you can use three special read-only parameters:
Testing around:
class Test(object):
def foo(self):
pass
instance = Test()
instance.foo # <bound method Test.foo of <__main__.Test object at 0x1>>
instance.foo.im_func # <function foo at 0x2>
instance.foo.im_self # <__main__.Test object at 0x1>
instance.foo.im_class # <__main__.Test class at 0x3>
# A few remarks
instance.foo.im_self.__class__ == instance.foo.im_class # True
instance.foo.__name__ == instance.foo.im_func.__name__ # True
instance.foo.__doc__ == instance.foo.im_func.__doc__ # True
# Now, note this:
Test.foo.im_func != Test.foo # unbound method vs function
Test.foo.im_self is None
# Let's play with classmethods
class Extend(Test):
@classmethod
def bar(cls):
pass
extended = Extend()
# Be careful! Because it's a class method, the class is returned, not the instance
extended.bar.im_self # <__main__.Extend class at ...>
There is an interesting thing to note here, that gives you a hint on how the methods are being called:
class Hint(object):
def foo(self, *args, **kwargs):
pass
@classmethod
def bar(cls, *args, **kwargs):
pass
instance = Hint()
# this will work with both class methods and instance methods:
for name in ['foo', 'bar']:
method = instance.__getattribute__(name)
# call the method
method.im_func(method.im_self, 1, 2, 3, fruit='banana')
Basically, im_self attribute of a bound method changes, to allow using it as the first parameter when calling im_func
You can use the __self__ property of a bound method to access the instance that the method is bound to.
>> a.__self__
<__main__.test object at 0x782d0>
>> a.__self__.b = 2
>> obj.b
2
You can also use the im_self property, but this is not forward compatible with Python 3.
>> a.im_self
<__main__.test object at 0x782d0>
since python2.6 synonyms for im_self and im_func are __self__ and __func__, respectively. im* attributes are completely gone in py3k. so you would need to change it to:
>> a.__self__
<__main__.test object at 0xb7b7d9ac>
>> a.__self__.b = 2
>> obj.b
2
