Rick van Hattem
41 lines
931 B
ReStructuredText
41 lines
931 B
ReStructuredText
# The metaclass definition, note the inheritance of type instead
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of object
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>>> class MetaSandwich(type):
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...
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... # Notice how the __new__ method has the same arguments
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... # as the type function we used earlier?
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... def __new__(metaclass, name, bases, namespace):
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... name = 'SandwichCreatedByMeta'
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... bases = (int,) + bases
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... namespace['lettuce'] = 1
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... return type.__new__(metaclass, name, bases, namespace)
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# First, the regular Sandwich:
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>>> class Sandwich(object):
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... pass
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>>> Sandwich.__name__
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'Sandwich'
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>>> issubclass(Sandwich, int)
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False
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>>> Sandwich.lettuce
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Traceback (most recent call last):
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...
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AttributeError: type object 'Sandwich' has no attribute 'lettuce'
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# Now the meta-Sandwich
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>>> class Sandwich(object, metaclass=MetaSandwich):
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... pass
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>>> Sandwich.__name__
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'SandwichCreatedByMeta'
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>>> issubclass(Sandwich, int)
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True
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>>> Sandwich.lettuce
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1
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