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Date: Thu, 8 Dec 2011 14:13:19 +1100
Subject: Re: Dynamic variable creation from string
From: Chris Angelico <rosuav@gmail.com>
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:16798

On Thu, Dec 8, 2011 at 11:03 AM, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> wrote:
>> It is really important that the scope of a,b,c is limited to the Sum
>> function, they must not exisit outside it or inside any other nested
>> functions.
>
> The second part is impossible, because that is not how Python works.
> Nested functions in Python can always see variables in their enclosing
> scope. If you don't want that behaviour, use another language, or don't
> use nested functions.

To the OP: By "nested functions", did you mean actual nested functions
(those defined inside this function), or simply functions called from
this one?

This is a nested function, as the term is usually taken to mean:

def outer_function():
    a = 1
    def inner_function():
        b = 2
        return a+b
    print(inner_function())  # Prints 3

The inner function has access to all of the outer function's
namespace. But if you meant this:

def function_1():
    b = 2
    return a+b

def function_2():
    a = 1
    print(function_1())

then it's quite the other way around - Python never shares variables
in this way (this would have function_1 assume that 'a' is a global
name, so if it's not, you'll get a run-time NameError).

As Steven says, there's no way in Python to hide variables from an
actual nested function. But if you just mean a function called from
this one, then what you want is the normal behaviour (and if you
actually want to share variables, you pass them as arguments).

ChrisA