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Re: I love assert

References (9 earlier) <87h9y4owgc.fsf@elektro.pacujo.net> <54669308$0$13002$c3e8da3$5496439d@news.astraweb.com> <87h9y1l3tt.fsf@elektro.pacujo.net> <mailman.15836.1416013493.18130.python-list@python.org> <87a93tl07u.fsf@elektro.pacujo.net>
Date 2014-11-15 12:48 +1100
Subject Re: I love assert
From Chris Angelico <rosuav@gmail.com>
Newsgroups comp.lang.python
Message-ID <mailman.15837.1416016126.18130.python-list@python.org> (permalink)

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On Sat, Nov 15, 2014 at 12:30 PM, Marko Rauhamaa <marko@pacujo.net> wrote:
> Chris Angelico <rosuav@gmail.com>:
>
>> On Sat, Nov 15, 2014 at 11:12 AM, Marko Rauhamaa <marko@pacujo.net> wrote:
>>> Most importantly, assertion failures are not supposed to be recovered
>>> from (within the program). Assertion failures can result in the loss
>>> of life and limb. They can result in database corruption. They can
>>> result in monetary losses. They can result in smoke coming out of the
>>> monitor.
>>
>> Or, in theory, AssertionError just prevented any of the above from
>> happening.
>
> I'd advice against catching AssertionError and trying to recover from it
> within the program. You could catch it, log it and reraise it, but since
> the failure modes could be completely unexpected (really, by
> definition), I would move fault-tolerance outside the failing process
> and try to restore a coherent reality from there.

I agree - never catch it. But you should be able to prevent database corruption:

conn = establish_database_connection()
try:
    do_stuff()
finally:
    conn.rollback()

The raising of AssertionError anywhere inside do_stuff() will prevent
craziness from getting to the database, because it aborts the
execution. (You know, the way a royal pardon does.)

ChrisA

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I love assert Peter Cacioppi <peter.cacioppi@gmail.com> - 2014-11-11 11:40 -0800
  Re: I love assert Ben Finney <ben+python@benfinney.id.au> - 2014-11-12 07:03 +1100
    Re: I love assert Grant Edwards <invalid@invalid.invalid> - 2014-11-11 21:43 +0000
  Re: I love assert Ethan Furman <ethan@stoneleaf.us> - 2014-11-11 12:08 -0800
  Re: I love assert Rob Gaddi <rgaddi@technologyhighland.invalid> - 2014-11-11 12:20 -0800
  Re: I love assert Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-11-11 20:34 +0000
  Re: I love assert TP <wingusr@gmail.com> - 2014-11-11 12:57 -0800
  Re: I love assert Terry Reedy <tjreedy@udel.edu> - 2014-11-11 17:34 -0500
  Re: I love assert Ben Finney <ben+python@benfinney.id.au> - 2014-11-12 09:52 +1100
  Re: I love assert Tim Chase <python.list@tim.thechases.com> - 2014-11-11 17:03 -0600
  Re: I love assert Peter Cacioppi <peter.cacioppi@gmail.com> - 2014-11-11 15:02 -0800
  Re: I love assert Ethan Furman <ethan@stoneleaf.us> - 2014-11-11 15:38 -0800
  Re: I love assert Dan Stromberg <drsalists@gmail.com> - 2014-11-11 17:56 -0800
  Re: I love assert Chris Angelico <rosuav@gmail.com> - 2014-11-12 13:21 +1100
  Re: I love assert Ben Finney <ben+python@benfinney.id.au> - 2014-11-12 13:35 +1100
    Re: I love assert Grant Edwards <invalid@invalid.invalid> - 2014-11-12 14:10 +0000
  Re: I love assert Chris Angelico <rosuav@gmail.com> - 2014-11-12 13:44 +1100
    Re: I love assert wxjmfauth@gmail.com - 2014-11-11 23:14 -0800
  Re: I love assert Terry Reedy <tjreedy@udel.edu> - 2014-11-12 03:29 -0500
  Re: I love assert Anton <anton.schattenfeld@gmail.com> - 2014-11-12 12:53 -0800
    Re: I love assert Marko Rauhamaa <marko@pacujo.net> - 2014-11-12 23:41 +0200
      Re: I love assert Ethan Furman <ethan@stoneleaf.us> - 2014-11-12 13:52 -0800
        Re: I love assert Marko Rauhamaa <marko@pacujo.net> - 2014-11-12 23:56 +0200
          Re: I love assert Ian Kelly <ian.g.kelly@gmail.com> - 2014-11-12 15:04 -0700
            Re: I love assert Anton <anschatten@gmail.com> - 2014-11-12 14:13 -0800
              Re: I love assert Ian Kelly <ian.g.kelly@gmail.com> - 2014-11-12 15:41 -0700
                Re: I love assert Anton <anschatten@gmail.com> - 2014-11-12 14:48 -0800
                Re: I love assert Marko Rauhamaa <marko@pacujo.net> - 2014-11-13 01:01 +0200
                Re: I love assert Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-11-15 10:40 +1100
                Re: I love assert Marko Rauhamaa <marko@pacujo.net> - 2014-11-15 02:12 +0200
                Re: I love assert Chris Angelico <rosuav@gmail.com> - 2014-11-15 12:04 +1100
                Re: I love assert Marko Rauhamaa <marko@pacujo.net> - 2014-11-15 03:30 +0200
                Re: I love assert Chris Angelico <rosuav@gmail.com> - 2014-11-15 12:48 +1100
                Re: I love assert Tim Chase <python.list@tim.thechases.com> - 2014-11-14 20:14 -0600
                Re: I love assert Chris Angelico <rosuav@gmail.com> - 2014-11-15 13:16 +1100
                Re: I love assert albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-11-29 17:35 +0000
                Re: I love assert Ian Kelly <ian.g.kelly@gmail.com> - 2014-11-12 16:02 -0700
                Re: I love assert Anton <anschatten@gmail.com> - 2014-11-12 15:43 -0800
                Re: I love assert Chris Angelico <rosuav@gmail.com> - 2014-11-13 10:10 +1100
                Re: I love assert Marko Rauhamaa <marko@pacujo.net> - 2014-11-13 01:23 +0200
                Re: I love assert Chris Angelico <rosuav@gmail.com> - 2014-11-13 10:27 +1100
                Re: I love assert Marko Rauhamaa <marko@pacujo.net> - 2014-11-13 01:31 +0200
              Re: I love assert Ethan Furman <ethan@stoneleaf.us> - 2014-11-12 14:47 -0800
                Re: I love assert Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-11-14 22:37 +1100
                Re: I love assert Ian Kelly <ian.g.kelly@gmail.com> - 2014-11-14 09:40 -0700
          Re: I love assert Ian Kelly <ian.g.kelly@gmail.com> - 2014-11-12 15:07 -0700
            Re: I love assert Marko Rauhamaa <marko@pacujo.net> - 2014-11-13 00:47 +0200
              Re: I love assert Ethan Furman <ethan@stoneleaf.us> - 2014-11-12 14:56 -0800
              Re: I love assert Chris Angelico <rosuav@gmail.com> - 2014-11-13 09:58 +1100
              Re: I love assert Ian Kelly <ian.g.kelly@gmail.com> - 2014-11-12 16:05 -0700
                Re: I love assert Marko Rauhamaa <marko@pacujo.net> - 2014-11-13 01:12 +0200
              Re: I love assert Lie Ryan <lie.1296@gmail.com> - 2014-11-14 01:09 +1100
        Re: I love assert Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-11-14 22:33 +1100
          Re: I love assert Ethan Furman <ethan@stoneleaf.us> - 2014-11-14 10:18 -0800
            Re: I love assert Marko Rauhamaa <marko@pacujo.net> - 2014-11-14 21:12 +0200
              Re: I love assert Ethan Furman <ethan@stoneleaf.us> - 2014-11-14 12:41 -0800
                Re: I love assert Marko Rauhamaa <marko@pacujo.net> - 2014-11-14 22:50 +0200
            Re: I love assert Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-11-15 13:58 +1100
              Re: I love assert Ethan Furman <ethan@stoneleaf.us> - 2014-11-14 20:09 -0800
                Re: I love assert Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-11-17 13:09 +1100
                Re: I love assert Ethan Furman <ethan@stoneleaf.us> - 2014-11-16 19:25 -0800
      Re: I love assert Anton <anschatten@gmail.com> - 2014-11-12 14:00 -0800
        Re: I love assert Anton <anschatten@gmail.com> - 2014-11-12 14:04 -0800
          Re: I love assert Marko Rauhamaa <marko@pacujo.net> - 2014-11-13 00:34 +0200
    Re: I love assert Chris Angelico <rosuav@gmail.com> - 2014-11-13 09:43 +1100
  Re: I love assert Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-11-14 22:15 +1100
  Re: I love assert Richard Riehle <rriehle@itu.edu> - 2014-11-14 14:09 -0800
    Decorators (was: Re: I love assert) Marko Rauhamaa <marko@pacujo.net> - 2014-11-15 00:18 +0200
      Re: Decorators Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-11-14 22:37 +0000
        Re: Decorators Marko Rauhamaa <marko@pacujo.net> - 2014-11-15 00:47 +0200
      Re: Decorators (was: Re: I love assert) Richard Riehle <rriehle@itu.edu> - 2014-11-14 18:19 -0800
        Re: Decorators (was: Re: I love assert) Mayank Tripathi <oquanox@gmail.com> - 2014-11-15 02:36 +0000
        Re: Decorators (was: Re: I love assert) Tim Chase <python.list@tim.thechases.com> - 2014-11-14 20:30 -0600
          Re: Decorators Marko Rauhamaa <marko@pacujo.net> - 2014-11-15 09:00 +0200
            Re: Decorators Grant Edwards <invalid@invalid.invalid> - 2014-11-15 15:32 +0000
        Re: Decorators (was: Re: I love assert) Richard Riehle <rriehle@itu.edu> - 2014-11-14 23:42 -0800
        Re: Decorators Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-11-15 13:12 +0000
          Re: Decorators Marko Rauhamaa <marko@pacujo.net> - 2014-11-15 15:24 +0200
            Re: Decorators Terry Reedy <tjreedy@udel.edu> - 2014-11-15 15:28 -0500
        Re: Decorators (was: Re: I love assert) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-11-16 02:39 +1100
  Re: I love assert TP <wingusr@gmail.com> - 2014-11-27 01:22 -0800
    Re: I love assert alister <alister.nospam.ware@ntlworld.com> - 2014-11-27 09:59 +0000
      Re: I love assert Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-11-29 12:30 +1100
        Re: I love assert MRAB <python@mrabarnett.plus.com> - 2014-11-29 02:56 +0000
          Re: I love assert Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-11-29 20:31 +1100
            Re: I love assert Chris Angelico <rosuav@gmail.com> - 2014-11-29 21:40 +1100
            Re: I love assert MRAB <python@mrabarnett.plus.com> - 2014-11-29 19:49 +0000
        Re: I love assert Chris Angelico <rosuav@gmail.com> - 2014-11-29 14:02 +1100
        Re: I love assert Ethan Furman <ethan@stoneleaf.us> - 2014-11-29 14:33 -0800
          Re: I love assert Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-11-30 19:18 +1100
            Re: I love assert Ethan Furman <ethan@stoneleaf.us> - 2014-11-30 11:34 -0800

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