On Tue, Oct 13, 2020 at 1:21 PM Christopher Barker <python...@gmail.com>
wrote:
> On Tue, Oct 13, 2020 at 9:55 AM David Mertz <me...@gnosis.cx> wrote:
>
>> If you really want a snazzy highly-parameterized exception, write it
>> yourself as a class factory. I won't particularly like the antipattern,
>> but it's available now.
>>
>> if some_bad_thing:
>> raise ExceptionMaker("BadStuffError", details, plus, more_details)
>>
>> Implementation of 'ExceptionMaker' left to readers. But it's possible to
>> write once.
>>
>
> raise ExceptionMaker.BadStuffError(details, plus, more_details)
>
> But here's where I am still completely confused. In order to catch that
> Exception, you need know about it -- it's name, what parameters it uses,
> etc.
> And that will be potentially very far from the code that creates it.
>
Yeah, I thought of that. I think the class factory would need to
monkey-patch the global namespace.
However, there's already a really clear way of "monkey-patching the global
namespace":
class BadStuffError(Exception): pass
Sure, you can accomplish the same thing by overloading .__getattr__(). But
the usual means is pretty nice.
The OP has stated that all making an Exception class does is create a name
> -- which is true (though the other thing it does is put that name in a
> class hierarchy) -- but the thing is -- that's very useful! In fact, I
> can't see how you could do this at all without creating a name somewhere
> that it could be accessed from elsewhere.
>
Well, technically you could memoize calls to ExceptionMaker and have this
work.
In [11]: try:
...: raise ExceptionMaker("BadStuffError")
...: except ExceptionMaker("BadStuffError"):
...: print("caught")
...:
caught
I am NOT recommending this pattern. But it works in current Python.
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