75 lines
2.1 KiB
Python
75 lines
2.1 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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from typing import Union, Any
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from collections.abc import Iterable, Iterator
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FieldNames = Union[str, Iterable[str]] # <1>
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def record_factory(cls_name: str, field_names: FieldNames) -> type[tuple]: # <2>
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slots = parse_identifiers(field_names) # <3>
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def __init__(self, *args, **kwargs) -> None: # <4>
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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) -> Iterator[Any]: # <5>
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for name in self.__slots__:
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yield getattr(self, name)
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def __repr__(self): # <6>
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values = ', '.join(
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'{}={!r}'.format(*i) for i in zip(self.__slots__, self)
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)
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cls_name = self.__class__.__name__
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return f'{cls_name}({values})'
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cls_attrs = dict( # <7>
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__slots__=slots,
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__init__=__init__,
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__iter__=__iter__,
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__repr__=__repr__,
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)
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return type(cls_name, (object,), cls_attrs) # <8>
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def parse_identifiers(names: FieldNames) -> tuple[str, ...]:
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if isinstance(names, str):
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names = names.replace(',', ' ').split() # <9>
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if not all(s.isidentifier() for s in names):
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raise ValueError('names must all be valid identifiers')
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return tuple(names)
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# end::RECORD_FACTORY[]
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