[Python-Dev] Very Strange Argument Handling Behavior (original) (raw)

Steven D'Aprano steve at pearwood.info
Sun Apr 18 00:21:57 CEST 2010

On Sun, 18 Apr 2010 07:47:08 am Maciej Fijalkowski wrote:

On Sat, Apr 17, 2010 at 1:03 PM, Steve Holden <steve at holdenweb.com> wrote: > Dino Viehland wrote: >> Maciej wrote: > > [...] > >>> And yet that breaks some code :-) >> >> Sure, if you do: >> >> class C(object): >>     locals()[object()] = 42 >> >> dir(C) >> >> You lose.  Once I'm aware of some piece of code in the wild doing >> this then I'll be happy to change IronPython to be more >> compatible. :) > > This would be a lose anyway, since the CPython specifications > suggest that you should not rely on being able to change locals() > (or at least shouldn't expect that such changes are actually > reflected in the local namespace).

You can override new of a type subclass to achieve the same effect (or even directly call type.new with strange dict as an argument).

I think that only works in Python 3.x, in 2.x the dict is always a regular dict no matter what you pass. At least for CPython. If there is a way to set the dict of a class to something other than a regular dict in CPython 2.x, I would be very pleased!

-- Steven D'Aprano

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