On 04-Dec-2012, at 10:23 AM, Anand Chitipothu <anandol...@gmail.com> wrote:
> On Tue, Dec 4, 2012 at 10:13 AM, Satyajit Ranjeev
> <satyajit.ranj...@gmail.com> wrote:
>> You are right in mentioning scopes.
>>
>> Lets take case 2:
>>
>> def f():
>> x = 1 # x is pointing to object 1
>>
>> class Foo:
>> print(x) # what you are doing is printing object 1
>> x = x + 1 # you are defining x in the class's scope and
>> pointing it to the object 2
>> print(x) # printing out the x in the class's scope
>>
>> print(x) # gives 1 as that's the object x is pointing in f()'s
>> scope
>> print(Foo.x) # gives 2 - the object x is pointing in Foo's scope
>>
>> f()
>
> No, this fails with an error.
>
> NameError: name 'x' is not defined
>
> It tries to find x in the global scope, not in the enclosed scope.
>
> If this is working for you, then you must have a global variable x
> defined. Try removing it.
You are right i did have a global x defined.
>
>> Take case 3:
>> def g():
>> y = 1
>> class Foo:
>> y = 2
>> def gety(self):
>> return y
>> foo = Foo()
>> print(y, foo.y, foo.gety())
>> # when you print y it prints the y in g()'s scope.
>> # when you print foo.y, you print y defined in Foo's scope.
>> # foo.gety() does not return Foo.y rather the y defined earlier in the
>> # method.
>> # If you print locals() in gety() you will get something similar to :
>> # {'y': 1, 'self': <__main__.Foo instance at 0x10c8041b8>, 'Foo': <class
>> __main__.Foo at 0x10c822bb0>}
>> # so what happens is that you are still accessing y of the functions scope.
>> # If you had returned self.y or a Foo.y it would have been different.
>>
>> g()
>>
>> I don't think the first two cases are weird. But yes, case 3 does seem a bit
>> weird especially while returning y in the method call.
>
> What is really weird is that the class body is evaluated without
> considering the enclosed scope, but the methods defined in the class
> have access to the enclosed scope.
>
I'm not sure if we should call it a weird behaviour, but I do agree its not
very intuitive. Accessing the class' attributes must be done with a prefix,
either self or the name of the class itself.
> Anand
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