Metaklasy w Pythonie

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#27125

From: pr
Date: Sun, 03 Jan 2010 22:40

37 lines
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Witam,

Czy da się tak zrobić aby "metaklasa była lazy", to znaczy, aby
wywołanie metody __new__ w MyMeta nastąpiło w wyniku świadomego
odwołania do klasy B (patrz kod niżej), czyli, np kiedy zrobię tak:
print B.myattr
print B().myattr
a nie w chwili gdy interpreter napotka już tylko samą definicję klasy
(czyli za każdym razem, niezależnie czy jej używam):
class B(A): pass
?

Z góry dzięki za odpoweidź.

class MyMeta(type):

    def __new__(cls, name, bases, attrs):
        print "Metaclass"
        super_new = super(MyMetal, cls).__new__
        parents = [b for b in bases if isinstance(b, MyMeta)]
        if not parents:
            return super_new(cls, name, bases, attrs)

        module = attrs.pop('__module__')
        new_class = super_new(cls, name, bases, {'__module__':
module})
        ...
        ...
        return new_class


class A(object):

    __metaclass__ = MyMeta

class B(A):
    pass

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From: pr <cricogik@gmail.com>
Newsgroups: pl.comp.lang.python
Subject: Metaklasy w Pythonie
Date: Sun, 3 Jan 2010 14:40:22 -0800 (PST)
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