global variables in imported modules

[Patrick Maupin]

On May 16, 4:42 pm, vsoler <vicente.so... at gmail.com> wrote:
> Taken fromwww.python.org, FAQ 2.3 How do I share global variables
> across modules?
>
> config.py:
>
> x = 0   # Default value of the 'x' configuration setting
>
> mod.py:
>
> import config
> config.x = 1
>
> main.py:
>
> import config       # try removing it
> import mod
> print config.x
>
> The example, such as shown in the website, works perfectly well.
> However, I don't fully understand why I have to import config in
> main.py, since it has already been imported by mod.py.
>
> As the website explains, there is only one module namespace for each
> module, and mod.py has aleady created the config namespace by
> importing it. Why should I import it again in main.py if that
> namespace already exists?
>
> If I remove ->   import config       # try removing it     in main.py,
> the application does not run
>
> What am I missing?

What you are missing is that the interpreter has to look *inside* a
namespace in order to actually find the object associated with a
name.  As you found out, there is a namespace per module.  So
main.py's namespace is where the code in main.py will search for
variables.  If 'mod' imports config, then the 'mod' module's namespace
is updated with 'config' -> the config module.  But the act of 'mod'
importing 'config' will not alter the namespace of 'main' at all.  So
if you want to access variable 'x' inside 'config' from main you can
either import config directly into main and access it as config.x, or
you can import config into mod and import mod into main and access it
as mod.config.x.

Regards,
Pat