Groups > comp.lang.python > #20220

Re: Postpone evaluation of argument

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From	88888 Dihedral <dihedral88888@googlemail.com>
Newsgroups	comp.lang.python
Subject	Re: Postpone evaluation of argument
Date	Sat, 11 Feb 2012 03:16:39 -0800 (PST)
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在 2012年2月11日星期六UTC+8上午7时57分56秒，Paul Rubin写道：
> Righard van Roy 
>  writes:
> > I want to add an item to a list, except if the evaluation of that item
> > results in an exception.
> 
> This may be overkill and probably slow, but perhaps most in the spirit
> that you're asking.
> 
>     from itertools import chain
> 
>     def r(x):
>         if x > 3:
>             raise(ValueError)
>         return x
> 
>     def maybe(func):
>       try:
>          yield func()
>       except:
>          return
> 
I am wondering at which level to yield in a nested decorated function
is more controllable. 

It is definitely wrong to yield in manny levels decorated.


>     def p(i): return maybe(lambda: r(i))
> 
>     your_list = list(chain(p(1), p(5)))
>     print your_list

Thread

Postpone evaluation of argument Righard van Roy <pluijzer@gmail.com> - 2012-02-11 00:01 +0100
  Re: Postpone evaluation of argument Paul Rubin <no.email@nospam.invalid> - 2012-02-10 15:57 -0800
    Re: Postpone evaluation of argument 88888 Dihedral <dihedral88888@googlemail.com> - 2012-02-11 03:16 -0800
  Re: Postpone evaluation of argument Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2012-02-11 10:54 +0200

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