[Python-ideas] Proposal: Abolition of bare except clauses

[Terry Reedy]

On 4/11/2015 7:29 AM, Chris Angelico wrote:
> A bare "except:" clause catches any exception. As of Python 3.0, this
> can be spelled more explicitly as "except BaseException:", and AFAIK
> the only difference between the two is that someone might rebind
> BaseException.
>
> String exceptions were abolished during the 2.x line, without causing
> major upheaval. The deprecation and ultimate abolition of the bare
> except syntax would have less consequence than that, as it would
> merely require a mechanical transformation to "except BaseException:",
> without needing any corresponding changes at raise site.

> Thoughts?

* There are about 20 bare excepts in idlelib and an issue (15313) to 
remove them by adding the missing class or tuple.  I have looked at a 
few and found it is hard to determine what should be added.  I may 
eventually just add Exception if I cannot be more specific (or general).

* 'except:' is easily caught by a code checker, or reported by grep. 
This works both ways: don't need to change the language, but equally 
easy to find to change if the language is changed.

* As Steven said, there could be a long deprecation period.

-- 
Terry Jan Reedy