returning True, False or None

[Brian van den Broek]

Alex Martelli said unto the world upon 2005-02-04 13:02:
> Steven Bethard <steven.bethard at gmail.com> wrote:
> 
> 
>>I have lists containing values that are all either True, False or None,
>>e.g.:
>>
>>     [True,  None,  None,  False]
>>     [None,  False, False, None ]
>>     [False, True,  True,  True ]
>>     etc.
>>
>>For a given list:
>>* If all values are None, the function should return None.
>>* If at least one value is True, the function should return True.
>>* Otherwise, the function should return False.
>>
>>Right now, my code looks like:

<SNIP OP's code>

>>This has a light code smell for me though -- can anyone see a simpler
>>way of writing this?
> 
> 
> What about...:
> 
> for val in lst:
>     if val is not None:
>         return val
> return None
> 
> or the somewhat fancy/clever:
> 
> for val in (x for x in lst if x is not None):
>     return val
> return None
> 
> 
> Alex

These don't do what the OP desired.

.>>> test_case = [False, True,  True,  True ]
.>>> def alexs_funct(lst):
.        for val in lst:
.            if val is not None:
.                return val
.        return None

 >>> alexs_funct(test_case)
False

But, by the 'spec', it ought return True.

Best,

Brian vdB
A mere newbie, quite pleased with himself for finding a problem with 
'bot code -- next scheduled to occur mid 2011 :-)