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Created April 25, 2018 03:35
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`functools.singledispatchmethod` for use before 3.8
from functools import singledispatch, update_wrapper
class singledispatchmethod:
"""Single-dispatch generic method descriptor.
Supports wrapping existing descriptors and handles non-descriptor
callables as instance methods.
def __init__(self, func):
if not callable(func) and not hasattr(func, "__get__"):
raise TypeError(f"{func!r} is not callable or a descriptor")
self.dispatcher = singledispatch(func)
self.func = func
def register(self, cls, method=None):
"""generic_method.register(cls, func) -> func
Registers a new implementation for the given *cls* on a *generic_method*.
return self.dispatcher.register(cls, func=method)
def __get__(self, obj, cls):
def _method(*args, **kwargs):
method = self.dispatcher.dispatch(args[0].__class__)
return method.__get__(obj, cls)(*args, **kwargs)
_method.__isabstractmethod__ = self.__isabstractmethod__
_method.register = self.register
update_wrapper(_method, self.func)
return _method
def __isabstractmethod__(self):
return getattr(self.func, '__isabstractmethod__', False)
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