[Python-Dev] Issue #26204: compiler now emits a SyntaxWarning on constant statement

[Guido van Rossum]

Personally I don't think it's worth the churn.

On Mon, Feb 8, 2016 at 5:49 PM, Chris Angelico <rosuav at gmail.com> wrote:
> On Tue, Feb 9, 2016 at 12:41 PM, MRAB <python at mrabarnett.plus.com> wrote:
>> On 2016-02-09 00:53, Guido van Rossum wrote:
>>>
>>> The warning for 'assert (cond, msg)' was specifically put in because
>>> this is a nasty trap. It's *always* a mistaken attempt to write
>>> 'assert cond, msg' -- usually in an attempt to break a long line
>>> without using a backslash. I'd actually consider promoting it to a
>>> syntax error rather than removing the warning.
>>>
>>> Compared to other "lint warnings" this one is much nastier -- it is
>>> also much more certain that it is a mistake. (Much more certain than
>>> e.g. an undefined variable, which could still be legitimate code due
>>> to dynamic updates to globals() or builtins.)
>>
>> Would there be less chance of confusion if there were some kind of syntax
>> such as "assert cond with msg"?
>
> Is assert the *only* statement that has a comma separating unrelated
> items? Every other statement that uses a comma is separating identical
> items (eg "import os, sys" - "os" and "sys" are equivalent), and
> tokens that have completely different meaning are separated by a word.
> The only other exception I can think of - pun intended - is the old
> "except BaseException, e:" syntax, which got dropped in Py3. Maybe
> it's time to introduce a new syntax with a view to deprecating the
> comma syntax ("use this old syntax if you need to support Python
> 2.7").
>
> +1.
>
> ChrisA
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-- 
--Guido van Rossum (python.org/~guido)