Re: [matplotlib-devel] propagation of error messages in matplotlib

[Steve C. <ste...@ya...>]

On Thu, 2004-11-18 at 18:05 +0000, Jochen Voss wrote: 
> 4) some ideas:
> 
>   - The backends could return errors via python standard exceptions
>     without printing messages and such.  This leads to simple code,
>     feels quite Pythonic, makes the backends more independent of the
>     error reporting policy and at the moment seems to be the only sane
>     solution to me.
> 
>   - The backends should have a function which the matlab interface can
>     call to report errors to the user.  This should pop up a dialog
>     etc.  on GUI backends and just print the message to stderr for
>     non-GUI backends.  It should not terminate the program.
I agree with these ideas.

> 7) Conclusions:
> 
>   I suggest the following.
> 
>   - Change backend_template.py and all the other non-GUI backends to
> 
> 	def error_msg_ps(msg, *args):
> 	    """
> 	    Signal an error condition.
> 	    """
> 	    sys.stderr.write('Error: %s' % msg)
I'd prefer to merge error_msg into the Verbose class, or just delete it.

>   - Change all callers of error_msg to terminate the program after the
>     call when appropriate
Agree

>   - Remove the verbose.report_error function and replace it with Python
>     exceptions etc.
Agree

> What do you think?
At the moment we have error_msg(), the Verbose class and exceptions all
working in the same area and a bit of confusion as to which one does
what. I don't think we need all three. 

I suggest
- using exceptions to handle errors that may terminate the program, and
allowing the matlab interface, GUI backends and user scripts to catch
these exceptions.
- using verbose for all reporting
- merging error_msg() into the Verbose class (with the GUI backends
possibly subclassing Verbose to provide a popup error dialog)

Steve