Catch all exceptions from an imported module

Question

I have got a program (a gui with kivy) which imports a non-standard module (made by one of my co-workers) which raises exceptions (Exception) for very particular issues. I wish to catch all raised Exception from that particular module so that I can raise a popup in my program. So what's the best way to catch raised exceptions from a particular module?

I tried this

toc is the module name

import toc
...
...
try:
    ...
    ...
except toc.Exception:
    ...

But this doesn't seem to work, it produces an AtrributeError saying that the module has no attribute 'Exception'. What am I doing wrong?

Edit: One more question:

If I have:

try:
    ...
    try:
        ....
    except:
        some small block code
except:
    some large block code

will the exception handling work within the local blocks? I mean if I get an error in the smaller block, will the error handling proceed to the the 'some small block code' or will it go to 'some large block code'?

Answer 1

You can catch all exceptions of specific type, but you need to give correct type. Your toc.Exception is not an exception class.

Generally you have three approaches, depending mainly on the module's design:

• if the module contains some common exception class (like it deals with some API and all API errors inherit from the base module class), catch every error using this class,
• if the module does not have such base error class, but has own exception classes, you can catch them all,

• if you want to catch every error (even like KeyError or ValueError), then you can try to do this:

  try:
      # ... some external module call ...
  except:
      # ... some exception handling ...
  

  (preferably for single calls, not for bigger blocks that are more likely to contain your module errors)

But you should be aware that this will not give you enough information in case of error (eg. you will have to guess that the function you are trying to call does not exist there).

Also make sure there is no other way to solve your problem. You are dangerously close to implementing Diaper Pattern and should avoid that by giving explicit classes for the exceptions you want to catch.

Answer 2

Don't do this in code you don't want to be embarrassed by, but this works:

import requests, inspect

exception_types = [obj for name, obj in inspect.getmembers(requests.exceptions) if inspect.isclass(obj) and issubclass(obj, Exception)]

try:
    raise requests.exceptions.HTTPError()
except Exception as e:
    if any(issubclass(e.__class__, lv) for lv in exception_types):
        print "This exception came from requests.exceptions"
    else:
        print "This exception came from somewhere else"
        raise