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Date: Sun, 2 Mar 2014 04:30:41 +1100
Subject: Re: Can global variable be passed into Python function?
From: Chris Angelico <rosuav@gmail.com>
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On Sun, Mar 2, 2014 at 4:23 AM, Marko Rauhamaa <marko@pacujo.net> wrote:
> Ben Finney <ben+python@benfinney.id.au>:
>
>> No. I'm telling you that =E2=80=98is=E2=80=99 is *wrong* for comparing s=
trings,
>> because it is unreliable.
>
> No, it isn't as long as the string object references have a common
> assignment "pedigree." Assignment (including parameter passing) is
> guaranteed to preserve identity of any object.

Of course it is, but your identity tests also depend on there NOT
being a common object when there is NOT an "assignment pedigree". The
positive is guaranteed; the negative is not. And if you don't care
about a false positive - that is, that some other string with the same
value matches - then what you actually want is equality, not identity,
comparison.

ChrisA