[Python-Dev] PEP 443 - Single-dispatch generic functions (original) (raw)

Ethan Furman ethan at stoneleaf.us
Thu May 23 20:38:05 CEST 2013

On 05/23/2013 11:13 AM, Éric Araujo wrote:

Thanks for writing this PEP. Blessing one implementation for the stdlib and one official backport will make programmers’ lives a bit easier :)

>>> @fun.register(int) ... def (arg, verbose=False): ... if verbose: ... print("Strength in numbers, eh?", end=" ") ... print(arg) ... Does this work if the implementation function is called like the first decorated function? (I don’t know the proper terminology) e.g. >>> @fun.register(int) ... def fun(arg, verbose=False): ... if verbose: ... print("Strength in numbers, eh?", end=" ") ... print(arg) The precedent is 2.6+ properties, where prop.setter mutates and returns the property object, which then overwrites the previous name in the class dictionary.

Actually, properties return new instances:

--> class Test(object): ... _temp = 'fleeting' ... @property ... def temp(self): ... return self._temp ... @temp.setter ... def new_temp(self, value): ... self._temp = value ...

--> id(Test.temp) 30245384

--> id(Test.new_temp) 30246352

--> Test.temp is Test.new_temp False

-- Ethan

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