[wxPython-users] Reload after an exception not possible ?

[Stef Mientki]

Tal Einat wrote:
> On 8/1/07, Stef Mientki <s.mientki at ru.nl> wrote:
>   
>> hello,
>>
>> I posted this question in the normal Python newsgroup,
>> because I think it's a normal Python question,
>> but I'm afraid that these kinds of constructs are only used in GUI.
>> So maybe here someone can give the answer.
>>     
>>> hello,
>>>
>>> I've a graphical application (wxPython),
>>> where the code in the main GUI loop is given below.
>>>
>>>
>>> 1    JAL_Loaded = False
>>> 2    while len(App_Running) > 0:
>>> 3        if JALsPy_globals.State == SS_Run:
>>> 4            try:
>>> 5                if JAL_Loaded:
>>> 6                    reload ( JAL_simulation_file )
>>> 7                else:
>>> 8                    JAL_Loaded = True
>>> 9                    import JAL_simulation_file
>>> 10           except JALsPy_globals.Reload_Exception:
>>> 11               JALsPy_globals.State = SS_Halt
>>>
>>>
>>> The first time the while loop is entered,
>>> JAL_Loaded is False (line 1),
>>> and when I press some button,
>>> the code will enter at line 8,
>>> importing a module, that has executable code with an infinite loop.
>>>
>>> To exit this infinite loop, an exception is generated (by a button
>>> press),
>>> and program comes back in the above while-loop line (10,11,2).
>>>
>>> So far so good.
>>>
>>> Then I change the code in the imported file,
>>> and when I start the engine again,
>>> the flag JAL_Loaded is True, so I don't import,
>>> but I reload the file.
>>>
>>> Now I get the next exception
>>>    UnboundLocalError: local variable 'JAL_simulation_file' referenced
>>> before assignment
>>>
>>> So obviously I can't reload but have to do an import again
>>> (which makes the code much simpler
>>> but I don't understand why the reload raises an exception ????
>>>
>>>       
>> thanks,
>> Stef Mientki
>>     
>
> Have you tried declaring JAL_simulation_file as global? I wonder if
> that would work...
>   
No,
but the solution is much simpler

2    while len(App_Running) > 0:
3        if JALsPy_globals.State == SS_Run:
4            try:
9                import JAL_simulation_file
10           except JALsPy_globals.Reload_Exception:
11               JALsPy_globals.State = SS_Halt

The second (and next) time I do the import at line 9,
it reloads the changed file perfectly.
But I don't understand it ;-)

cheers,
Stef