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

[MRAB]

On 2016-02-08 23:21, Chris Barker wrote:
> On Mon, Feb 8, 2016 at 1:51 PM, Victor Stinner <victor.stinner at gmail.com
> <mailto:victor.stinner at gmail.com>> wrote:
>
>     I didn't know. I just checked. It's assert used with a non-empty tuple:
>
>      >>> assert ("tuple",)
>
>
> which is more interesting with a tuple without the parentheses:
>
> t = In [*4*]: t = True,
>
> In [*5*]: t
>
> Out[*5*]: (True,)
>
> works fine, but not if you use an assert:
>
> In [*7*]: assert True,
>
>    File "<ipython-input-7-38940c80755c>", line 1
>
>      assert True,
>
>                  ^
>
> SyntaxError:invalid syntax
>
> I actually like the Warning with the note about the problem better:
>
>     <stdin>:1: SyntaxWarning: assertion is always true, perhaps remove
>     parentheses?
>
>
> And, of course, more relevant with something Falsey in the tuple:
>
> In [*14*]: assert (False,)
>
> <ipython-input-14-05f425f558c4>:1: SyntaxWarning: assertion is always
> true, perhaps remove parentheses?
>
>    assert (False,)
>
> But I am curious why you get a different error without the parens?
>
Try:

     help('assert')

You'll see that in "assert (True,)", the tuple (an object) is the first 
condition (and probably a mistake), whereas in "assert True,", the True 
is the condition and the second expression (after the comma) is missing.