[Python-ideas] Specify an alternative exception for "assert"

[Ryan Gonzalez]

Other than the fact that this would completely fail when run with -O...

I believe I brought this up a while back (~1-2 years), and that was the
reply.

--
Ryan
[ERROR]: Your autotools build scripts are 200 lines longer than your
program. Something’s wrong.
http://kirbyfan64.github.io/
On May 2, 2016 9:23 AM, "Giampaolo Rodola'" <g.rodola at gmail.com> wrote:

> assert statement gives the possibility to display the text which goes
> along with the AssertionError exception. Most of the times though, what
> would be more appropriate is to raise a different exception (e.g.
> ValueError). My proposal is to be able to specify an exception as a
> replacement for AssertionError as in:
>
> >>> assert callable(fun), ValueError("object is not a callable")
> ValueError: object is not a callable
>
> Specifically, this would be useful at the top of a function or method,
> where argument types or values are usually checked:
>
> def retry(times=3, timeout=0.1, callback=None):
>     assert times >= 1, ValueError("times must be >= 1")
>     assert isinstance(timeout, (int, float)), ValueError("invalid timeout")
>     assert callable(callback), ValueError("callback is not a callable")
>
> ...as opposed to:
>
> def retry(times=3, timeout=0.1, callback=None):
>     if not times >= 1:
>         raise ValueError("times must be >= 1")
>     if not isinstance(timeout, (int, float)):
>         raise ValueError("invalid timeout")
>     if not callable(callback):
>         raise ValueError("callback is not a callable")
>
> Other than saving 1 line for each type/value check, this has the advantage
> that the assertion logic (e.g. "times >= 1") is shown in the traceback
> message itself, because it's on the same line, enriching the context and
> giving more information in case of error.
>
> Thoughts?
>
> --
> Giampaolo - http://grodola.blogspot.com
>
>
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