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Piotr Maślanka authored938a7b31
Exceptions and warnings
For you to use
Warnings
CustomException
This is the class you can base your exceptions off. It provides a reasonable __repr__ and __str__, eg.:
class MyException(CustomException):
...
assert str(MyException) == 'MyException()'__repr__ will additionally prefix the exception class name with entire module path to it.
CodedCustomException
A CustomException with an additional field in constructor, namely the exception's code, and a special property that it's subclasses who define a class property code are considered instances of that class, if it's code matches.
Example:
class BaseCodedError(CodedCustomException):
def __init__(self, msg, code):
super().__init__(msg, code)
class Code2Error(BaseCodedError):
code = 2
assert isinstance(BaseCodedError('message', 2', Code2Error)The exceptions have to be in a common hierarchy to check them via codes.
For example, the following is true:
- ::
-
- class DifferentHierarchy(CodedCustomException):
- pass
assert not isinstance(DifferentHierarchy('message', 2), Code2Error)
In general, please do not construct direct exceptions from CodedCustomException, please do it via a hierarchy such as:
class GenericError(CodedCustomException):
pass
class SpecificError(GenericError):
code = 3
raise SpecificError('message')Note that this won't allow you to handle exceptions like that
try:
raise BaseCodedError('message', 2')
except Code2Error:
self.succeed()
else:
self.fail()As this is a Python limitation.
The CodedCustomException uses the following metaclass to accomplish it's magic
ImpossibleError
Note that ImpossibleError inherits from BaseException instead of the standard Satella hierarchy. The thought is, since this is an anomalous exception, it should get to the top of the stack ASAP.