49 lines
850 B
Python
49 lines
850 B
Python
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#!/usr/bin/env python3
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class Wrong:
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def __init_subclass__(subclass):
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subclass.__slots__ = ('x', 'y')
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class Klass0(Wrong):
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pass
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o = Klass0()
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o.z = 3
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print('o.z = 3 # did not raise Attribute error because __slots__ was created too late')
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class Correct1(type):
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def __new__(meta_cls, cls_name, bases, cls_dict):
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cls_dict['__slots__'] = ('x', 'y')
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return super().__new__(
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meta_cls, cls_name, bases, cls_dict)
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class Klass1(metaclass=Correct1):
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pass
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o = Klass1()
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try:
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o.z = 3
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except AttributeError as e:
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print('Raised as expected:', e)
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class Correct2(type):
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def __prepare__(name, bases):
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return dict(__slots__=('x', 'y'))
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class Klass2(metaclass=Correct2):
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pass
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o = Klass2()
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try:
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o.z = 3
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except AttributeError as e:
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print('Raised as expected:', e)
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