[Tutor] “has a value of True” versus “evaluates true” (was: don't understand iteration)

Clayton Kirkwood crk at godblessthe.us
Tue Nov 11 21:04:05 CET 2014

So, there is a difference between None and False, is that the issue? I don’t necessarily see the difference as stated in the subject line. 


If  A == True

If A


Is this the crux of the issue?


BTW, the feedback to my submittal suggests that this is a difference with no distinction.




From: wesley chun [mailto:wescpy at gmail.com] 
Sent: Monday, November 10, 2014 11:35 PM
To: crk at godblessthe.us
Cc: Ben Finney; tutor
Subject: Re: [Tutor] “has a value of True” versus “evaluates true” (was: don't understand iteration)


good catch, and definitely a distinction beginners should be more cognizant of.

it's also good to recognize that a call to "bool(match)" would render that statement correct, as the built-in/factory function will return what an object evaluates to (True [re.match object] or/vs.False [None]).


On Mon, Nov 10, 2014 at 5:31 PM, Clayton Kirkwood <crk at godblessthe.us> wrote:

I reported it. I feel all grown up now. Kind of like one of the boys(girls...)


>-----Original Message-----
>From: Tutor [mailto:tutor-bounces+crk <mailto:tutor-bounces%2Bcrk> =godblessthe.us at python.org] On
>Behalf Of Ben Finney
>Sent: Monday, November 10, 2014 3:24 PM
>To: tutor at python.org
>Subject: [Tutor] “has a value of True” versus “evaluates true” (was:
>don't understand iteration)
>"Clayton Kirkwood" <crk at godblessthe.us> writes:
>> Also of confusion, the library reference says:
>> Match objects always have a boolean value of True. Since match() and
>> search() return None when there is no match, you can test whether
>> there was a match with a simple if statement:
>> match = re.search(pattern, string)
>> if match:
>>     process(match)
>The documentation is incorrect, as you point out: “have a boolean value
>of True” implies that the value is identical to the built-in ‘True’
>constant, which is never the case for these objects.
>Instead, the passage above should say “evaluates true in a boolean
>Would you be so kind as to report a bug to that effect
> \       “The Vatican is not a state.… a state must have people. There |
>  `\    are no Vaticanians.… No-one gets born in the Vatican except by |
>_o__)        an unfortunate accident.” —Geoffrey Robertson, 2010-09-18 |
>Ben Finney
>Tutor maillist  -  Tutor at python.org
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