[Python-ideas] Default return values to int and float

[Michael Foord]

On 7 October 2011 20:18, Jim Jewett <jimjjewett at gmail.com> wrote:

> On Thu, Oct 6, 2011 at 6:04 PM, Terry Reedy <tjreedy at udel.edu> wrote:
> > On 10/6/2011 4:32 PM, Jim Jewett wrote:
> >> On Wed, Oct 5, 2011 at 5:17 PM, Terry Reedy<tjreedy at udel.edu>  wrote:
> >>> On 10/4/2011 10:21 PM, Guido van Rossum wrote:
>
> >>>> We also have str.index which raised an exception, but people dislike
> >>>> writing try/except blocks.
>
> >>> ... try/except blocks are routinely used for flow control in Python
> >>> ... even advocate using them over if/else (leap first)
>
> >> str.index is a "little" method that it is tempting to use inline, even
> >> as part of a comprehension.
>
> > That is an argument *for* raising an exception on error.
>
> Only for something that is truly an unexpected error.  Bad or missing
> data should not prevent the program from processing what it can.
>
> When I want an inline catch, it always meets the following criteria:
>
> (a)  The "exception" is actually expected, at least occasionally.
> (b)  The exception is caused by (bad/missing/irrelevant...) input --
> nothing is wrong with my computational environment.
> (c)  I do NOT need extra user input; I already know what to do with it.
>
> Typically, I just filter it out, though I may replace it with a
> placeholder and/or echo it to another output stream instead.
>
> (d)  The algorithm SHOULD continue to process the remaining (mostly good)
> data.
>
>
> Sometimes, the "bad" data is itself in a known format (like a "."
> instead of a number); but ... not always.
>
>
Yeah, I've quite often worked on data sets where you just need to process
what you can and ignore (or replace with placeholders) what you can't.

Michael Foord


> -jJ
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