62 lines
2.0 KiB
Python
62 lines
2.0 KiB
Python
"""
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record_factory: create simple classes just for holding data fields
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# tag::RECORD_FACTORY_DEMO[]
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>>> Dog = record_factory('Dog', 'name weight owner') # <1>
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>>> rex = Dog('Rex', 30, 'Bob')
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>>> rex # <2>
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Dog(name='Rex', weight=30, owner='Bob')
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>>> name, weight, _ = rex # <3>
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>>> name, weight
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('Rex', 30)
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>>> "{2}'s dog weighs {1}kg".format(*rex) # <4>
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"Bob's dog weighs 30kg"
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>>> rex.weight = 32 # <5>
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>>> rex
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Dog(name='Rex', weight=32, owner='Bob')
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>>> Dog.__mro__ # <6>
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(<class 'factories.Dog'>, <class 'object'>)
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# end::RECORD_FACTORY_DEMO[]
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The factory also accepts a list or tuple of identifiers:
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>>> Dog = record_factory('Dog', ['name', 'weight', 'owner'])
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>>> Dog.__slots__
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('name', 'weight', 'owner')
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"""
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# tag::RECORD_FACTORY[]
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def record_factory(cls_name, field_names):
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try:
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field_names = field_names.replace(',', ' ').split() # <1>
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except AttributeError: # no .replace or .split
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pass # assume it's already a sequence of strings
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field_names = tuple(field_names) # <2>
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if not all(s.isidentifier() for s in field_names):
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raise ValueError('field_names must all be valid identifiers')
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def __init__(self, *args, **kwargs): # <3>
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attrs = dict(zip(self.__slots__, args))
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attrs.update(kwargs)
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for name, value in attrs.items():
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setattr(self, name, value)
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def __iter__(self): # <4>
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for name in self.__slots__:
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yield getattr(self, name)
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def __repr__(self): # <5>
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values = ', '.join('{}={!r}'.format(*i) for i
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in zip(self.__slots__, self))
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return '{}({})'.format(self.__class__.__name__, values)
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cls_attrs = dict(__slots__ = field_names, # <6>
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__init__ = __init__,
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__iter__ = __iter__,
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__repr__ = __repr__)
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return type(cls_name, (object,), cls_attrs) # <7>
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# end::RECORD_FACTORY[]
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