The problem is that exceptions raised by the inputsplitter are not handled
by IPython. I've asked at IPython-devel
at http://python.6.x6.nabble.com/InputSplitter-and-SyntaxError-td5025938.html
but didn't get an answer so far.
On Thursday, July 25, 2013 10:46:00 AM UTC-4, William wrote:
>
> On Wed, Jul 24, 2013 at 10:02 AM, Robert Bradshaw
> <robe...@math.washington.edu <javascript:>> wrote:
> > On Wed, Jul 24, 2013 at 6:00 AM, Simon King
> > <simon...@uni-jena.de<javascript:>>
> wrote:
> >> Hi!
> >>
> >> On 2013-07-24, Volker Braun <vbrau...@gmail.com <javascript:>> wrote:
> >>> Upstream does not allow the input transformer to fail, so either its a
> >>> not-yet-implemented feature in IPython or we are abusing the IPython
> >>> mechanism to parse the input where only trivial transformations should
> be
> >>> done. Can you post this to the ipython mailinglist?
> >>
> >> What's the problem? Nobody forces us to let the preparser raise an
> >> error. So, instead of raising an error, the preparser should simply
> >> return the malformed input string, and then it is ipython's job to
> raise
> >> the error.
> >
> > But if one has something like "R.<x> = QQ[)" then the syntax error at
> > the first . rather than the correct location. IMHO, IPython should let
> > the input transformer reject input.
>
> +1
>
> Without doing what you suggest there is no way to give a really
> meaningful error message to the user.
> This would be especially bad if it were a whole block of code! For
> example,
>
> R.<x> = QQ[]
> [50 lines of code]
> S.<t> = QQ{]
>
> If we just passed it back to IPython unpreparsed, then the error would
> be in line 1, since that's not valid Python.
> What we want is to clearly indicate that the error is in the line with
> the error.
>
> That said, in this particular case:
>
> preparse('R.<t> = QQ{]')
>
> outputs something that looks like a bug in the preparser implementation:
>
> ...
> opening = constructor.rindex('[')
> ValueError: substring not found
>
> If anything, it should be raising a SyntaxError, right?
>
> William
>
> >
> > - Robert
> >
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> >
>
>
>
> --
> William Stein
> Professor of Mathematics
> University of Washington
> http://wstein.org
>
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