[Tutor] Time to Use a Global Variable?

[Kent Johnson]

Rich Shepard wrote:
>    In my wxPython application the UI is run out of class MyFrame. The method
> associated with File->Quit is called OnFileQuit. All the code for pysqlite is
> in another class called DBinterface, and that has a method closeDB():
> 
>    def closeDb(self):
>      """
>      Closes the database connection explicitly.
>      """
>      self.cur.close()
>      self.con.close()
> 
>    OnFileQuit looks like this:
> 
>    def OnFileQuit(self, event):
>      closeDb()
>      fn.close()
>      self.Close()
> 
>    When I test the application and try to close it, python complains
>    File "eikos.py", line 315, in OnFileQuit
>      closeDb()
> NameError: global name 'closeDb' is not defined
> 
>    I've tried changing OnFileQuit to call DBinterface.closeDB(), but that
> doesn't work. Obviously I still haven't completely grokked how to refer in
> one class to a method defined in another class. Of course, I've not
> explicitly created an instance of DBinterface within MyFrame, so that may be
> the problem.

Evidently closeDb is an instance method of some class you don't show 
here. Does DBinterface create and maintain a single instance of this 
class? or some other code creates an instance?

You need to call closeDb on the DBinterface instance, it is not a 
module-level function. You haven't shown enough code for me to know how 
the OnFileQuit method might gain access to the DBinterface instance; how 
do you access other methods for working with the database?

Kent