Can module access global from __main__?

[Steve Holden]

Neal Becker wrote:
> Suppose I have a main program, e.g., A.py.  In A.py we have:
> 
> X = 2
> import B
> 
> Now B is a module B.py.  In B, how can we access the value of X?
> 
> 
Without trying in any way to dodge the question, why do you want to do that?

There's a property of software called "coupling" that's used to describe 
the way that communications take place between different components of a 
piece of software. Ideally modules should be loosely-coupled, which is 
usually achieved by passing values in as function or method arguments 
and receiving the results as the return values of said functions or methods.

When a module is loosely-coupled in this way it's possible to revise the 
structure of one component completely (while maintaining the same 
interface specification) without affecting any other component.

By introducing some magic "load a variable from the namespace of the 
importing module" you make your modules tightly-coupled, which is very 
bad for maintainability: what happens if you now import B.py into a 
module that doesn't create an X in its namespace?

The fact that you ask the question implies that you really need to think 
a little harder about the structure of your program. If you tell us the 
*real* problem (back to my "why do you want to do that" question ...) 
perhaps we can suggest a better-structured solution.

regards
  Steve

PS: If A is the main program (the module that you have run) then you 
should be able to access it as __main__.X, but you'd be *very naughty* 
to do so :-)
-- 
Steve Holden       +44 150 684 7255  +1 800 494 3119
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