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To: python-list@python.org
From: Terry Reedy <tjreedy@udel.edu>
Subject: Re: Dict when defining not returning multi value key error
Date: Thu, 31 Jul 2014 15:17:53 -0400
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Xref: csiph.com comp.lang.python:75435

On 7/31/2014 7:24 AM, Dilu Sasidharan wrote:

> I am wondering why the dictionary in python not returning multi value
> key error when i define something like
>
> p =3D {'k':"value0",'k':"value1"}

This is documented behavior: "you can specify the same key multiple=20
times in the key/datum list, and the final dictionary=E2=80=99s value for=
 that=20
key will be the last one given." I am not sure whether this is an=20
accident of the initial design, never changed since, or intended for=20
certain uses.  It may partly be because this choice is slightly simpler=20
or, since keys are expressions, not constants, that the check can only=20
come at runtime.

 >>> def f(x): return 0

 >>> {f(1):1, f(2):2}
{0: 2}

--=20
Terry Jan Reedy