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Date: Wed, 14 Dec 2011 13:05:19 +0100
From: Jean-Michel Pichavant <jeanmichel@sequans.com>
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To: Chris Angelico <rosuav@gmail.com>
Subject: Re: Overriding a global
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Chris Angelico wrote:
> On Wed, Dec 14, 2011 at 9:14 PM, Jean-Michel Pichavant
> <jeanmichel@sequans.com> wrote:
>   
>> The problem makes little sense when using names like x or func1. Besides
>> namespace issues, naming 2 *different objects* with the same meaningful name
>> is usually a bad idea and points the fact that your names are no that
>> meaningful.
>>     
>
> So... it's a bad idea for me to use 'i' many times in my code, with
> the same name having different meanings in different places? In
> languages with infinitely-nesting scopes (one of Python's great lacks,
> imho), I've often had three different variables with the same names,
> all perfectly valid, and all doing what they should. It's not just
> loop indices - I used to have a piece of code in which 'res' was a
> MySQL resource being processed in a loop, and I had three nested
> loops. Each time I referenced 'res', it used the innermost available
> resource, which was precisely what I wanted. If I'd arbitrarily had to
> guarantee that all variable names were unique, I would have had
> completely unnecessary fiddling around.
>
> Python wouldn't let you do that with three nested 'res'es in one
> function, but you can perfectly reasonably have a global and a local.
> It makes perfect sense... which is a good reason for keeping it legal.
>
> ChrisA
>   

Bad ideas :

i = 5

def spam():
  for i,v in enumerate([1,2,3,4]):
    for i,v in enumerate(['a','b', 'c']):
      print i, v
    print i,v # bad surprise


good ideas :

# global
nameThatWillNotBeUsedlocally = 'foo'

def spam():
  for qtyIndex, quantity in enumerate([5,6,3,1]):
    for fruitIndex, fruit in enumerate(['orange', 'banana']):
      print fruitIndex, fruit
    print qtyIndex, quantity

While a lot of people still use i,j,k,v to handler values and indexes, I 
think it's a bad idea. I'm just stating an opinion from my personnal 
python experience. I know some people can successfully use the hard way.

JM