Importing variables non-deterministic?

[Antoon Pardon]

Op 19-08-13 09:45, Dave Angel schreef:
> Antoon Pardon wrote:
> 
>> Op 17-08-13 17:01, Steven D'Aprano schreef:
>>>
>>> And here you re-import the name "y" from struct_global. That rebinds the 
>>> current module's "y" with whatever value struct_global.y has *now*, 
>>> rather than a second (or a minute, or an hour) earlier when the first 
>>> import took place. Obviously at some point between the first import and 
>>> the second import, struct_global.y must have been reassigned from -1 to 
>>> 62.
>>>
>>> This goes to show why global variables are considered harmful, and why 
>>> clean, modern program design tries to reduce the use of them as much as 
>>> possible. Global variables are too easily modified by, well, *anything*. 
>>> The sort of behaviour you are seeing is sometimes called "action at a 
>>> distance" -- something, anything, anywhere in your program, possibly 
>>> buried deep, deep down inside some function you might never suspect, is 
>>> changing the global variable.
>>
>> I think you are overstating your case. Classes and functions are
>> variables too and in general nobody seems to have a problem with them
>> being global.
>>
> 
> It's global *variables* that are to be avoided.  constants like clsases
> and functions are fine.  On the other hand, class attributes can be
> variable, and thus are to be avoided when reasonable.

Python has no constants. Classes and functions can be changed just like
any other variable. I agree that classes and function are generally
meant to be constant, but often enought so are global int variables.

And some of those that do change, only do so in the initialisation phase
and should be considered constant for the rest of the program.

My point was that Steven has no way of knowing what exactly is going on
here and so shouldn't be making such a sweeping statement.

-- 
Antoon Pardon