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Re: What arguments are passed to the __new__ method ?

From eryk sun <eryksun@gmail.com>
Newsgroups comp.lang.python
Subject Re: What arguments are passed to the __new__ method ?
Date 2016-03-01 15:09 -0600
Message-ID <mailman.83.1456866603.20602.python-list@python.org> (permalink)
References <56d5d043$0$632$426a74cc@news.free.fr> <nb4u0g$tes$1@ger.gmane.org>

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On Tue, Mar 1, 2016 at 2:27 PM, Terry Reedy <tjreedy@udel.edu> wrote:
> On 3/1/2016 12:24 PM, ast wrote:
>
>> class Premiere:
>>     def __init__(self, price):
>>          pass
>> p = Premiere(1000)
>>
>> which is OK.
>
> Premiere is callable because it inherits object.__call__.  That function, or
> the implementation of the CALL FUNCTION bytecode, must notice that
> Premiere.__new__ is object.__new__, by inheritance, and only pass Premiere
> and not 1000.

It's not handled in bytecode or __call__. In CPython the type_call
function passes its args and kwds to the type's tp_new and tp_init
functions without modification. object.__new__ ignores the excess
arguments in this case, as described in my previous message.

While I think the cases where object.__new__ and object.__init__
ignore excess arguments are practical and sensible, they should still
be documented. AFAICT, the language reference has nothing to say on
this matter.

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Thread

What arguments are passed to the __new__ method ? "ast" <nomail@invalid.com> - 2016-03-01 18:24 +0100
  Re: What arguments are passed to the __new__ method ? eryk sun <eryksun@gmail.com> - 2016-03-01 13:54 -0600
  Re: What arguments are passed to the __new__ method ? Terry Reedy <tjreedy@udel.edu> - 2016-03-01 15:27 -0500
  Re: What arguments are passed to the __new__ method ? eryk sun <eryksun@gmail.com> - 2016-03-01 15:09 -0600
  Re: What arguments are passed to the __new__ method ? "ast" <nomail@invalid.com> - 2016-03-02 10:23 +0100
    Re: What arguments are passed to the __new__ method ? Steven D'Aprano <steve@pearwood.info> - 2016-03-02 22:02 +1100
  Re: What arguments are passed to the __new__ method ? Peter Pearson <pkpearson@nowhere.invalid> - 2016-03-02 17:40 +0000
    Re: What arguments are passed to the __new__ method ? Rob Gaddi <rgaddi@highlandtechnology.invalid> - 2016-03-02 17:57 +0000
      Re: What arguments are passed to the __new__ method ? Ian Kelly <ian.g.kelly@gmail.com> - 2016-03-02 11:26 -0700

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