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Groups > comp.lang.python > #5250

Re: Proper way to handle errors in a module

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On 2011.05.11 01:05 PM, Roy Smith wrote:
> You want to raise specific errors.  Let's say you've got a function like 
> this:
>
> def airspeed(swallow):
>    speeds = {"european": 42,
>              "african", 196}
>    return speeds[swallow]
>
> If somebody passes an invalid string, it will raise KeyError as written.  
> Better to do something like:
>
> def airspeed(swallow):
>    speeds = {"european": 42,
>              "african", 196}
>    try:
>        return speeds[swallow]
>    except KeyError:
>         raise UnknownBirdError(swallow)
Is there any way to do this without purposely setting up the code to
trigger an arbitrary exception if the function can't do its job? That
is, can I raise an UnknownBirdError outside of an except clause, and if
so, how? I can't find much help for doing this in Python 3, even in the
official docs.

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Proper way to handle errors in a module Andrew Berg <bahamutzero8825@gmail.com> - 2011-05-11 12:29 -0500
  Re: Proper way to handle errors in a module Roy Smith <roy@panix.com> - 2011-05-11 14:05 -0400
    Re: Proper way to handle errors in a module Andrew Berg <bahamutzero8825@gmail.com> - 2011-05-12 14:14 -0500
    Re: Proper way to handle errors in a module MRAB <python@mrabarnett.plus.com> - 2011-05-12 20:25 +0100
    Re: Proper way to handle errors in a module Andrew Berg <bahamutzero8825@gmail.com> - 2011-05-12 15:12 -0500
    Re: Proper way to handle errors in a module Corey Richardson <kb1pkl@aim.com> - 2011-05-12 16:20 -0400
    Re: Proper way to handle errors in a module Tycho Andersen <tycho@tycho.ws> - 2011-05-12 15:26 -0500
      Re: Proper way to handle errors in a module Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-05-13 00:43 +0000
    Re: Proper way to handle errors in a module MRAB <python@mrabarnett.plus.com> - 2011-05-12 21:26 +0100
    Re: Proper way to handle errors in a module Ethan Furman <ethan@stoneleaf.us> - 2011-05-12 13:40 -0700
    Re: Proper way to handle errors in a module Andrew Berg <bahamutzero8825@gmail.com> - 2011-05-12 15:35 -0500
      Re: Proper way to handle errors in a module Ben Finney <ben+python@benfinney.id.au> - 2011-05-13 10:56 +1000

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