exceptions.rst

Extended doctests for exceptions

raises

Allowed exceptions must inherit from the given base exception.

>>> raises(BaseException)
Traceback (most recent call last):
  ...
ValueError: allowed exceptions must inherit from the given base class (Exception); BaseException does not

>>> raises(Exception)
Traceback (most recent call last):
  ...
ValueError: allowed exceptions must inherit from the given base class (Exception); Exception does not

Exceptions which do not inherit from base are allowed to raise normally.

>>> @raises(ConnectionError, base=OSError)
... def f(exc):
...     raise exc

>>> f(BrokenPipeError)  # Subclass of ConnectionError
Traceback (most recent call last):
  ...
BrokenPipeError

>>> f(BlockingIOError)  # Subclass of OSError
Traceback (most recent call last):
  ...
exceptions.UnexpectedException: BlockingIOError

>>> f(ValueError)  # Not a subclass of OSError
Traceback (most recent call last):
  ...
ValueError

You can allow Exceptions, but don't do that.

>>> @raises(Exception, base=BaseException)
... def y_tho(exc):
...     raise exc

>>> y_tho(Exception)
Traceback (most recent call last):
  ...
Exception

>>> y_tho(KeyboardInterrupt)
Traceback (most recent call last):
  ...
exceptions.UnexpectedException: KeyboardInterrupt

>>> y_tho(SystemExit)
Traceback (most recent call last):
  ...
exceptions.UnexpectedException: SystemExit

>>> y_tho(BaseException)
Traceback (most recent call last):
  ...
exceptions.UnexpectedException: BaseException