From the PEP:
> A tool will be provided to automatically update code to replace bare except: with except BaseException:.
> A tool will be provided to automatically update code to replace bare except: with except BaseException:.
I have sometimes not run a Python script for a few years, and then when I need it, it stopped working and I need to track down what changed/broke or run some tool or whatnot. I don't keep track of the latest greatest Python changes – like most Python programmers it's not my "day job" to write Python code so I now need to track what changed between "the Python version I used about 3 years ago, whatever that was" and now. It's pretty annoying.
And that's assuming said tool will be fool-proof. Never mind of course that all my dependencies (if any) will need updating too.
What will happen in practice is that people will write "except Exception:" rather than "except:" and do nothing different. Basically nothing will change.
Meanwhile, I have C and Go programs that have worked without modification for about 10 years. Not that nothing ever breaks in C or Go, but it's the exception (hah!) rather than the rule.
I’d love to know whether that’s true, and to what extreme. I believe you’re right - that people using Python for a few hours a week (or less) greatly outnumber software developers using it as their primary language.
I think that’s a real issue for the evolution of Python, because updates to the language design (e.g. the makeup of the Steering Council) come almost entirely from the second group.
Yes I agree, and it's disappointing to see some take such a narrow view of things.
A big part of maintaining and evolving a language is saying "no" a lot. There are a lot of people with ideas, almost always reasoned from their own use-case. That's okay, everyone does that to some degree, but there almost always trade-offs and such to consider.
Your job as Steering Council or Core Dev or BFDL or whatever governance you have is to consider all use cases and make a balanced decision. Reading that thread, some do. But unfortunately others don't.
Even for Python 3, Guido spent most of his time saying "no" to proposals. There were a lot of pretty wild ideas for Python 3000.
I propose a rider to the PEP in which implementation will be deferred until its proponents can correctly affirm that the library reference lists, for each function and method, every exception it might throw.
No, the goal is a system in which the code correctly indicates which exceptions it's intended to handle, and doesn't accidentally handle the wrong exceptions because the developer was either lazy or misinformed about the semantics (perhaps due to experience with a different programming language).
What support does Python offer, to the author of a function, for determining what would be the wrong exceptions for it to handle? How, in Python, does the author of a function signal, to the functions she is calling, which exceptions they should not handle? As I alluded to in my previous post, the Python language and documentation does not even give programmers a good accounting of what exceptions the library functions might throw.
Other languages, notably Java, have tried the "functions document what they can raise" idea. Everyone seems to hate the result.
I know it is not nearly on the same level, but people seriously overestimate the effort needed between not doing anything at all and even the slightest work, no matter how reliable and easy. The difference between nothing and anything is huge.