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Re: dict to boolean expression, how to?

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On 01/08/2014 14:28, Steven D'Aprano wrote:
> On Fri, 01 Aug 2014 12:45:12 +0000, Alex van der Spek wrote:
>
>> With a dict like so:
>>
>> cond = {'a': 1, 'b': 1, 'c': 1,
>>          'A': 0, 'B', 0, 'C':0}
>>
>> how would you make a boolean expression like this:
>>
>> bool = (('a' == 1) & ('A' == 0) |
>>          ('b' == 1) & ('B' == 0) |
>>          ('c' == 1) & ('C' == 0))
>
> That's False. It's always False, because 'a' does not equal 1, etc. Also,
> you're using bitwise operators & and | rather than boolean operators.
> Finally, you are shadowing the built-in bool() type, which is probably a
> bad idea.
>
> In the first case, I think you mean cond['a'] == 1 rather than just
> 'a'==1; in the second case, the bool operators are called "and" and "or";
> and in the third case, there are many equally good names for a generic
> boolean flag, like "flag".
>
> Putting those together, I think you probably mean something like this:
>
> flag = (
>      (cond['a'] == 1 and cond['A'] == 0) or
>      (cond['b'] == 1 and cond['B'] == 0) or
>      (cond['c'] == 1 and cond['C'] == 0)
>      )
>
> which can be simplified to:
>
> flag = any( cond[c] == 1 and cond[c.upper()] for c in ['a', 'b', 'c'] )
>

Shouldn't that be cond[c.upper()] == 0 ?

-- 
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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dict to boolean expression, how to? Alex van der Spek <zdoor@xs4all.nl> - 2014-08-01 12:45 +0000
  Re: dict to boolean expression, how to? Chris Angelico <rosuav@gmail.com> - 2014-08-01 23:04 +1000
  Re: dict to boolean expression, how to? Roy Smith <roy@panix.com> - 2014-08-01 09:24 -0400
  Re: dict to boolean expression, how to? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-08-01 13:28 +0000
    Re: dict to boolean expression, how to? Roy Smith <roy@panix.com> - 2014-08-01 09:32 -0400
      Re: dict to boolean expression, how to? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-08-01 15:02 +0000
        Re: dict to boolean expression, how to? Terry Reedy <tjreedy@udel.edu> - 2014-08-01 18:16 -0400
    Re: dict to boolean expression, how to? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-08-01 16:50 +0100
      Re: dict to boolean expression, how to? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-08-01 16:35 +0000
  Re: dict to boolean expression, how to? Alex van der Spek <zdoor@xs4all.nl> - 2014-08-01 14:26 +0000
    Re: dict to boolean expression, how to? marco.nawijn@colosso.nl - 2014-08-01 08:07 -0700
    Re: dict to boolean expression, how to? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-08-01 15:24 +0000
      Re: dict to boolean expression, how to? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-08-01 17:03 +0100
    Re: dict to boolean expression, how to? Peter Otten <__peter__@web.de> - 2014-08-01 17:44 +0200
      eval [was Re: dict to boolean expression, how to?] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-08-02 02:59 +0000
        Re: eval [was Re: dict to boolean expression, how to?] Peter Otten <__peter__@web.de> - 2014-08-02 09:43 +0200
        Re: eval [was Re: dict to boolean expression, how to?] Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-08-02 08:59 +0100
        Re: eval [was Re: dict to boolean expression, how to?] Duncan Booth <duncan.booth@invalid.invalid> - 2014-08-05 11:57 +0000
          Re: eval [was Re: dict to boolean expression, how to?] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-08-06 02:25 +1000
    Re: dict to boolean expression, how to? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-08-01 17:12 +0100
    Re: dict to boolean expression, how to? Peter Pearson <ppearson@nowhere.invalid> - 2014-08-01 17:00 +0000
  Re: dict to boolean expression, how to? Ned Batchelder <ned@nedbatchelder.com> - 2014-08-01 10:29 -0400

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