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Groups > comp.lang.python > #101060
| From | Mark Lawrence <breamoreboy@yahoo.co.uk> |
|---|---|
| Newsgroups | comp.lang.python |
| Subject | Re: raise None |
| Date | 2015-12-31 15:58 +0000 |
| Message-ID | <mailman.109.1451577564.11925.python-list@python.org> (permalink) |
| References | <56847239$0$1590$c3e8da3$5496439d@news.astraweb.com> |
On 31/12/2015 00:09, Steven D'Aprano wrote: > I have a lot of functions that perform the same argument checking each time: > > def spam(a, b): > if condition(a) or condition(b): raise TypeError > if other_condition(a) or something_else(b): raise ValueError > if whatever(a): raise SomethingError > ... > > def eggs(a, b): > if condition(a) or condition(b): raise TypeError > if other_condition(a) or something_else(b): raise ValueError > if whatever(a): raise SomethingError > ... > > Since the code is repeated, I naturally pull it out into a function: > > def _validate(a, b): > if condition(a) or condition(b): raise TypeError > if other_condition(a) or something_else(b): raise ValueError > if whatever(a): raise SomethingError > > def spam(a, b): > _validate(a, b) > ... > > def eggs(a, b): > _validate(a, b) > ... > > But when the argument checking fails, the traceback shows the error > occurring in _validate, not eggs or spam. (Naturally, since that is where > the exception is raised.) That makes the traceback more confusing than it > need be. I disagree. > > So I can change the raise to return in the _validate function: > > def _validate(a, b): > if condition(a) or condition(b): return TypeError > if other_condition(a) or something_else(b): return ValueError > if whatever(a): return SomethingError > > and then write spam and eggs like this: > > def spam(a, b): > ex = _validate(a, b) > if ex is not None: raise ex > ... > > It's not much of a gain though. I save an irrelevant level in the traceback, > but only at the cost of an extra line of code everywhere I call the > argument checking function. > > But suppose we allowed "raise None" to do nothing. Then I could rename > _validate to _if_error and write this: > > def spam(a, b): > raise _if_error(a, b) > ... > > > and have the benefits of "Don't Repeat Yourself" without the unnecessary, > and misleading, extra level in the traceback. > > Obviously this doesn't work now, since raise None is an error, but if it did > work, what do you think? > A lot of fuss over nothing. -- My fellow Pythonistas, ask not what our language can do for you, ask what you can do for our language. Mark Lawrence
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raise None Steven D'Aprano <steve@pearwood.info> - 2015-12-31 11:09 +1100
Re: raise None Paul Rubin <no.email@nospam.invalid> - 2015-12-30 16:19 -0800
Validation in Python (was: raise None) Ben Finney <ben+python@benfinney.id.au> - 2015-12-31 11:26 +1100
Re: raise None Chris Angelico <rosuav@gmail.com> - 2015-12-31 11:38 +1100
Re: raise None Steven D'Aprano <steve@pearwood.info> - 2015-12-31 12:26 +1100
Re: raise None Ben Finney <ben+python@benfinney.id.au> - 2015-12-31 12:44 +1100
Re: raise None Steven D'Aprano <steve@pearwood.info> - 2015-12-31 15:07 +1100
Re: raise None Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2015-12-31 12:19 +0000
Re: raise None Steven D'Aprano <steve@pearwood.info> - 2016-01-01 02:35 +1100
Re: raise None Chris Angelico <rosuav@gmail.com> - 2016-01-01 02:53 +1100
Re: raise None Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2015-12-31 16:46 +0000
Re: raise None Steven D'Aprano <steve@pearwood.info> - 2016-01-01 04:50 +1100
Re: raise None "Martin A. Brown" <martin@linux-ip.net> - 2015-12-31 09:30 -0800
Re: raise None Ben Finney <ben+python@benfinney.id.au> - 2016-01-01 07:18 +1100
Re: raise None Johannes Bauer <dfnsonfsduifb@gmx.de> - 2016-01-02 12:47 +0100
Re: raise None Chris Angelico <rosuav@gmail.com> - 2016-01-01 09:48 +1100
Re: raise None Steven D'Aprano <steve@pearwood.info> - 2016-01-04 16:19 +1100
Re: raise None Dan Sommers <dan@tombstonezero.net> - 2016-01-04 06:09 +0000
Re: raise None Rustom Mody <rustompmody@gmail.com> - 2016-01-03 22:39 -0800
Re: raise None Ben Finney <ben+python@benfinney.id.au> - 2016-01-01 10:27 +1100
Re: raise None Marko Rauhamaa <marko@pacujo.net> - 2016-01-01 02:29 +0200
Re: raise None Steven D'Aprano <steve@pearwood.info> - 2016-01-04 16:19 +1100
Re: raise None Rustom Mody <rustompmody@gmail.com> - 2016-01-03 21:53 -0800
Re: raise None Rustom Mody <rustompmody@gmail.com> - 2016-01-04 03:55 -0800
Re: raise None Rustom Mody <rustompmody@gmail.com> - 2016-01-03 21:53 -0800
Re: raise None Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-12-31 23:36 +0000
Re: raise None Chris Angelico <rosuav@gmail.com> - 2016-01-01 10:39 +1100
Re: raise None Chris Angelico <rosuav@gmail.com> - 2016-01-01 10:41 +1100
Re: raise None Rustom Mody <rustompmody@gmail.com> - 2016-01-03 19:04 -0800
Re: raise None Chris Angelico <rosuav@gmail.com> - 2016-01-04 14:31 +1100
Re: raise None Steven D'Aprano <steve@pearwood.info> - 2016-01-04 14:48 +1100
Re: raise None Chris Angelico <rosuav@gmail.com> - 2016-01-04 14:56 +1100
Re: raise None Rustom Mody <rustompmody@gmail.com> - 2016-01-03 20:46 -0800
Re: raise None Christian Gollwitzer <auriocus@gmx.de> - 2016-01-04 08:28 +0100
Re: raise None Chris Angelico <rosuav@gmail.com> - 2015-12-31 13:12 +1100
Re: raise None Cameron Simpson <cs@zip.com.au> - 2015-12-31 15:03 +1100
Re: raise None Steven D'Aprano <steve@pearwood.info> - 2015-12-31 16:12 +1100
Re: raise None Cameron Simpson <cs@zip.com.au> - 2015-12-31 16:45 +1100
Re: raise None Terry Reedy <tjreedy@udel.edu> - 2015-12-30 23:00 -0500
Re: raise None Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-12-31 15:58 +0000
Re: raise None Johannes Bauer <dfnsonfsduifb@gmx.de> - 2015-12-31 17:17 +0100
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