True of False

Marc 'BlackJack' Rintsch bj_666 at gmx.net
Thu Sep 27 19:54:23 CEST 2007


On Thu, 27 Sep 2007 17:06:30 +0000, Duncan Booth wrote:

> Marc 'BlackJack' Rintsch <bj_666 at gmx.net> wrote:
> 
>> In [268]: 'c' in a == True
>> Out[268]: False
>> 
>> In [269]: ('c' in a) == True
>> Out[269]: True
>> 
>> In [270]: 'c' in (a == True)
>> -----------------------------------------------------------------------
>> ---- 
>><type 'exceptions.TypeError'>             Traceback (most recent call
>>last) 
>> 
>> /home/bj/<ipython console> in <module>()
>> 
>><type 'exceptions.TypeError'>: argument of type 'bool' is not iterable
>> 
>> 
>> What's going on there?
> 
> See http://docs.python.org/ref/comparisons.html
> 
>> Comparisons can be chained arbitrarily, e.g., x < y <= z is equivalent
>> to x < y and y <= z, except that y is evaluated only once (but in both
>> cases z is not evaluated at all when x < y is found to be false). 
> 
> In exactly the same way:
> 
>    'c' in a == True
> 
> is equivalent to:
> 
>    'c' in a and a == True
> 
> which is False.

Aaah *enlightenment*, I'm using this for range checks like in the docs,
but it wasn't obvious to me in this case.  Thanks.

Ciao,
	Marc 'BlackJack' Rintsch



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