73 lines
1.7 KiB
Python
73 lines
1.7 KiB
Python
# BEGIN MODEL_V5
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import abc
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class AutoStorage: # <1>
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__counter = 0
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def __init__(self):
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cls = self.__class__
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prefix = cls.__name__
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index = cls.__counter
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self.storage_name = '_{}:{}'.format(prefix, index)
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cls.__counter += 1
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def __get__(self, instance, owner):
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if instance is None:
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return self
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else:
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return getattr(instance, self.storage_name)
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def __set__(self, instance, value):
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setattr(instance, self.storage_name, value) # <2>
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class Validated(abc.ABC, AutoStorage): # <3>
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def __set__(self, instance, value):
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value = self.validate(instance, value) # <4>
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super().__set__(instance, value) # <5>
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@abc.abstractmethod
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def validate(self, instance, value): # <6>
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"""return validated value or raise ValueError"""
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INVALID = object()
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class Check(Validated):
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def __init__(self, checker):
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super().__init__()
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self.checker = checker
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if checker.__doc__ is None:
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doc = ''
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else:
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doc = checker.__doc__ + '; '
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self.message = doc + '{!r} is not valid.'
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def validate(self, instance, value):
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result = self.checker(value)
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if result is INVALID:
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raise ValueError(self.message.format(value))
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return result
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class Quantity(Validated): # <7>
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def validate(self, instance, value):
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if value <= 0:
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raise ValueError('value must be > 0')
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return value
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class NonBlank(Validated):
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def validate(self, instance, value):
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value = value.strip()
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if len(value) == 0:
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raise ValueError('value cannot be empty or blank')
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return value # <8>
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# END MODEL_V5
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