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48 lines
1.6 KiB
48 lines
1.6 KiB
2 years ago
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# coding: utf-8
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from functools import singledispatch, update_wrapper
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class singledispatchmethod:
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"""Single-dispatch generic method descriptor.
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Supports wrapping existing descriptors and handles non-descriptor
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callables as instance methods.
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"""
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def __init__(self, func):
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if not callable(func) and not hasattr(func, "__get__"):
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raise TypeError(f"{func!r} is not callable or a descriptor")
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self.dispatcher = singledispatch(func)
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self.func = func
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def register(self, cls, method=None):
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"""generic_method.register(cls, func) -> func
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Registers a new implementation for the given *cls* on a *generic_method*.
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"""
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return self.dispatcher.register(cls, func=method)
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def __get__(self, obj, cls=None):
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def _method(*args, **kwargs):
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if args:
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method = self.dispatcher.dispatch(args[0].__class__)
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else:
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method = self.func
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for v in kwargs.values():
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if v.__class__ in self.dispatcher.registry:
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method = self.dispatcher.dispatch(v.__class__)
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if method is not self.func:
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break
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return method.__get__(obj, cls)(*args, **kwargs)
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_method.__isabstractmethod__ = self.__isabstractmethod__
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_method.register = self.register
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update_wrapper(_method, self.func)
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return _method
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@property
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def __isabstractmethod__(self):
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return getattr(self.func, '__isabstractmethod__', False)
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