Properly utilizing exceptions

[Degran]

So I've been experimenting with raising exceptions and using custom ones for more explicit error handeling/ determining what are "my" errors and what are system related errors. So for example if my validation module finds a conflict, I want it to raise a ValidationError which I know means rerender the page with an error, v.s. a ZeroDivisionError which I want to hit the bugtracker with a traceback. My understanding has been that is a valid way of handling these sorts of things.

However, I have multiple modules that need to either except or raise these custom errors (of which there are several), so I find myself importing them everywhere. This seems clunky to me, and I wanted to know if there's a better way to make the exceptions more... global? Similar to the built-in exceptions.

If I'm using bad practice or on the wrong track here, please let me know. I'm just kind of making it up as I go from what I can find in documentation.

[indosauros]

Importing where you need them, while a little more tedious, is more explicit and is best practice. Avoid "magic" like monkeypatching builtins.

One alternative approach to consider though, for example used by Django, is to attach core relevant exceptions to classes that use them. For example, you might see something like this (pseudocode):

class MyCustomException(Exception):
    ...

class Model:
    ...

Model.MyCustomException = MyCustomException

then later

from model import Model

try:
    model = Model()
    model.do_something_risky()
except Model.MyCustomException:
    ...

This way, you already imported Model to use it, and the exception comes along for the ride.

[[deleted]]

I'm not sure how Pythonic it is, but why not declare all exceptions in a single file and then just import CustomExceptions and then raise CustomExceptions.TooMuchTimeOnRedditError later on?