Importing variables non-deterministic?

[Antoon Pardon]

Op 19-08-13 11:18, Chris Angelico schreef:
> On Mon, Aug 19, 2013 at 10:03 AM, Antoon Pardon
> <antoon.pardon at rece.vub.ac.be> wrote:
>> This is irrelevant. That some context defines a constant, and that you
>> can use a variable with the same name as a constant in python, doesn't
>> contradict the statement that python (as a language) doesn't has
>> constants. There is nothing in the language that would prevent buggy
>> code from changing any of those variables. So from a python point of
>> views these are just global variables. Just as the struct_global.y was
>> in the original contribution.
> 
> And there's nothing preventing a program from using ctypes to
> overwrite an object's refcount, thus causing a segfault. So?

Yes so? What is your point? Since Cpython caches small integers
there is probably nothing preventing a program from using ctypes
to make the number three behave as the number five. That doesn't
mean that the language define three and five to be equal.

A language having constants, does mean that the language can prevent
a name from being reassigned.

> The issue
> was regarding imports, and it's perfectly safe to import a constant,
> even if the interpreter doesn't protect you from then being a total
> idiot and changing it.

Python doesn't have constants, so you statement about importing a
constant doesn't make sense. The point is that python doesn't provide
the mechanism for protecting names against reassignments. So you
don't know whether the variable you think of as a constant is so
in reality. And this from a pure language definition point of view.
That you can use tools that make the interpreter no longer behave
as the language should, doesn't negate that.

-- 
Antoon Pardon.