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Re: scope of function parameters

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Henry




On 2011-05-29, at 5:47 , Wolfgang Rohdewald wrote:

> On Sonntag 29 Mai 2011, Henry Olders wrote:
>> It seems that in Python, a variable inside a function is
>> global unless it's assigned.
> 
> no, they are local
> 
>> I would have thought that a function parameter would
>> automatically be considered local to the function. It doesn't
>> make sense to me to pass a global to a function as a
>> parameter.
> 
> it is local. But consider what you actually passed:
> You did not pass a copy of the list but the list itself.
> You could also say you passed a reference to the list.
> All python variables only hold a pointer (the id) to
> an object. This object has a reference count and is
> automatically deleted when there are no more references
> to it.
> 
> If you want a local copy of the list you can either
> do what you called being ugly or do just that within
> the function itself - which I think is cleaner and
> only required once.
> 
> def fnc2(c):
> 		c = c[:]
>        c[1] = 'having'
>        return c

Thank you, Wolfgang. That certainly works, but to me it is still a workaround to deal with the consequence of a particular decision. From my perspective, a function parameter should be considered as having been assigned (although the exact assignment will not be known until runtime), and as an assigned variable, it should be considered local.

Henry

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Re: scope of function parameters Henry Olders <henry.olders@mcgill.ca> - 2011-05-29 16:19 -0400
  Re: scope of function parameters Christopher Head <chead@is.invalid> - 2011-05-29 14:48 -0700

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