Python type hinting with exceptions
PythonPython 3.xExceptionType HintingPython TypingPython Problem Overview
I have a function that looks like this:
def check_for_errors(result):
if 'success' in result:
return True
if 'error' in result:
raise TypeError
return False
In successful run of this function, I should get a bool, but if there is an error I should get a TypeError- which is OK because I deal with it in another function.
My function first line looks like this:
def check_for_errors(result: str) -> bool:
My question is: Should I mention the error in my type hinting?
Python Solutions
Solution 1 - Python
Type hinting can't say anything about exceptions. They are entirely out of scope for the feature. You can still document the exception in the docstring however.
From PEP 484 -- Type Hints:
> ## Exceptions > No syntax for listing explicitly raised exceptions is proposed. Currently the only known use case for this feature is documentational, in which case the recommendation is to put this information in a docstring.
Guido van Rossum has strongly opposed adding exceptions to the type hinting spec, as he doesn't want to end up in a situation where exceptions need to be checked (handled in calling code) or declared explicitly at each level.
Solution 2 - Python
It is usually a good idea to document the error. This means that another developer using your function will be able to handle your errors without having to read through your code.
Solution 3 - Python
i usually use:
def check_for_errors(result: str) -> bool | YourException: