[wxPython-users] Accessing Variable Across Modules

[Dan Cherry]

Rich Shepard wrote:
>   Both Robin and Chris wrote in response to one of my questions that
> supporting functions should be in modules separate from the main
> application. I'm trying to do this, but run into a problem with the 
> scope of
> a variable. Let me try to briefly explain.
> 
>   A.py contains the class MainFrame() and the entire wxPython UI. The
> File->New and File->Open menus call the bound functions, OnFileNew() and
> OnFileOpen() in the MainFrame class. These set the filename variable,
> 'projname,' that is the name of the project's SQLite3 database to be opened
> or created. In other words, a.py is the master module that imports all the
> other modules.
> 
>   One of these other modules is b.py. It holds a single class with the
> SQLite3 functions to open, create, and close the database connection. These
> functions need the 'projname' variable, but b.py is not within the scope of
> projname.
> 
You could pass 'projname' to b.py as a parameter when you instantiate 
the class (assuming that can happen after the UI has determined what the 
projname will be), and assign that value in your b.py class _init_ to 
something like 'self.projname'.  This would make it available to 
everything within that instance of b.py during subsequent calls.

In my opinion, the more variables you pass by parameter and access by 
functional returns, the more reliable your modules and functions will 
be, and the less you will have to keep straight in your head while 
programming.  Others may disagree.

>   My understanding of variable scope is that projname is local to
> OnFileOpen() and OnFileNew(), global within the class MainFrame(), and
> enclosing within the a.py module. But, since it's not a built in variable
> it's not visible to b.py. Of course, I cannot import a.py into b.py because
> that sets up a circular reference.
> 
>   What is the appropriate way to handle this situation? I moved the 
> database
> functions back into the MainFrame() class, but then had difficulties
> getting a pysqlite2 cursor from another module.
> 
> Rich
> 


-- 
Dan Cherry
dscherry (@) bellsouth.net

Finding a solution to a problem doesn't solve the problem...
Implementing the solution solves the problem.