I thought of a third advantage to this approach: Except clauses will be easier to understand.
If I'm reading someone's code and I see `except ValueError`, I'm gonna have to do a bit of thinking to figure out what exactly they're catching. On the other hand, if the code is `except IntParsingError`, then I know exactly what it is they're catching. On Fri, May 1, 2020 at 9:48 AM Ram Rachum <r...@rachum.com> wrote: > Hi, > > Here's something I wanted in Python for many years. If this has been > discussed in the past, please refer me to that discussion. > > On one hand, it's something that I can't imagine the python-dev community > supporting. On the other hand, it would maintain backward compatibility. > > I wish there were a 100 more built-in exceptions in Python, that will be > very specific about what went wrong. > > If I do this: > > >>> x, y = range(3) > > I know it'll raise a ValueError, because I've memorized that, but it did > take me a few years to remember where I should expect ValueError and where > I should expect TypeError. > > It would be nice if the operation above raised UnpackingOverflowError, > which will be a subclass of UnpackingError, along with > UnpackingUnderflowError. UnpackingError can be a subclass of ValueError, > for backward compatibility. > > Similarly, if I did this: > > >>> def f(x, y): return x + y > >>> f(1) > > I would get a TypeError. Would be a lot cooler if I got > MissingArgumentsError, which would be a subclass of SignatureError, which > would be a subclass of TypeError. > > There are 2 reasons I want this: > > 1. When I'm writing a try..except clause, I want to catch a specific > exception like MissingArgumentsError rather than ValueError or TypeError. > They're too ubiquitous. I don't want some other unexpected failure > producing the same ValueError and triggering my except clause. > > 2. When I get an error, especially from some shitty corporate system that > truncates the traceback, I want to get as many hints as possible about what > went wrong. > > It's true that today, most Python exceptions have good text in their > message, like "TypeError: f() missing 1 required positional argument: 'y'". > But that isn't guaranteed everywhere, and specific exception types could > help. > > > What do you think? > > > Ram. >
_______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-le...@python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/6Z2XITLJ4RSAW4WGTVPCA2YSHXONM3HO/ Code of Conduct: http://python.org/psf/codeofconduct/
