Question

I found this question while i searched the usage of metaclass in python.It’s a good question with a wonderful answer,See Here.But while i followed the example like this:

class UpperAttrMetaclass(type): 

    def __new__(cls, name, bases, dct):

        attrs = ((name, value) for name, value in dct.items() if not name.startswith('__'))
        uppercase_attr = dict((name.upper(), value) for name, value in attrs)

        return type.__new__(cls, name, bases, uppercase_attr)
class Foo(object):
    __metaclass__=UpperAttrMetaclass
    bar = 'bip'

Then:

print(hasattr(Foo,'bar'))

I was hoping it would output False,but instead it was True
It seems the metaclass didn’t change anything at all.
I must have made a mistake.Glad if you can point it out to me!

EDIT:
I was using IDLE 3.2,to make my situation more clear.

EDIT:
Thanks for all the answers.And i found a good post on this.So i post it hereMetaclass in python 2&3

Answer 1

You made no mistake. print(hasattr(Foo,'bar')) and print dir(Foo) give me:

False
['BAR', '__class__', ...

What’s your Python version? Mine is 2.7.2

If you use Python 3.x, try removing the __metaclass__ attribute and declaring your class as

class Foo(object, metaclass=UpperAttrMetaclass):
    ...