Can global variable be passed into Python function?

Steven D'Aprano steve+comp.lang.python at pearwood.info
Sat Mar 1 18:07:16 CET 2014


On Sat, 01 Mar 2014 22:59:52 +1100, Chris Angelico wrote:

> On Sat, Mar 1, 2014 at 10:28 PM, Marko Rauhamaa <marko at pacujo.net>
> wrote:
>> Ben Finney <ben+python at benfinney.id.au>:
>>
>>> Use ‘==’, since that's all that matters for getting a value that will
>>> work fine.
>>
>> You are telling me to use '==' if I choose string objects and 'is' if I
>> choose some other objects.
>>
>> I prefer a solution that works regardless of what objects I choose for
>> identifiers.
>>
>> There really is no taboo against string object identity if you know
>> what you are doing.
> 
> And, as proven here in this thread, you do not know what you are doing.

Steady on, that's a bit harsh. In context, I think that Marko is assuming 
that the caller will only ever use the state values via their symbolic 
names, e.g. only refer to them as IDLE, CONNECTED etc. and never use 
their internal string values "IDLE", "CONNECTED".

I don't think that's a safe assumption, since it requires the caller to 
only ever do the right thing, but if it is true, then using "is" in the 
way he suggests cannot fail.

Still, I've repeatedly asked Marko to justify why we should care about 
the symbols being singletons, and unless I've missed something, he hasn't 
even attempted to justify that. It seems to me that he's just assuming 
that symbols ought to be singletons, hence his focus on identity rather 
than equality.




-- 
Steven D'Aprano
http://import-that.dreamwidth.org/



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