question about True values
steve at holdenweb.com
Sat Oct 28 04:13:42 CEST 2006
J. Clifford Dyer wrote:
> I do see how mapping to Truth/Falsehood is more natural, and I do
> believe that one of the great things about python is that it feels
> natural in so many ways, and hence makes it easy to produce code, but
> the one thing that Ms. Creighton points out that I can't get past is
> that Python, even with its bool type, *still* evaluates somethingness
> and nothingness, and True and False are just numbers with hats on.
> >>> True + 3
> >>> bool(True-1)
> >>> bool(True-2)
> >>> (10 > 5) + (10 < 5)
> So when you say
> >>>if 10 > 5:
> .... print "Yes!"
Seems pretty clear to me that the situations you discuss above involve
numeric coercions of a Boolean value.
> Python is not evaluating the truth of the matter, but, as Ms. Creighton
> would say, the "somethingness" of that which 10 > 5 evaluates to. (1
> aka True)
It does seem that there is a specific type associated with the result of
a comparison, even though you would really like to to be "a number with
a hat on".
> Furthermore, how do you explain this bizarreness in terms of "Truth" and
> "Falsehood?" You have to go back to the fact that True=1 and that
> REALLY, Python is dealing with somethingness and nothingness. It might
> not be as direct a mental connection as True/False, but it is certainly
> a more accurate one for understanding how Python works.
> >>> (1 > 0) < 1
> >>> 1 > 0 < 1
> >>> 1 > (0 < 1)
> >>> 10 > (0 < 1)
I have no idea what you think that you are demonstrating here.
> Finally, while True/False is a good mental mapping for numeric
> comparisons, take the following:
> >>> if "Cliff is a pillar of the open source community":
> .... print "thank you"
> .... else:
> .... print "bugger off"
> bugger off
> Clearly this is not true. (Google Cliff/Dyer open source: only 11
> hits.), but the string is *something* so the if block gets evaluated.
>>> if "The above example was bollocks":
... print "You don't know what you are talking about"
... print "Sorry: of course you are perfectly correct"
You don't know what you are talking about
Steve Holden +44 150 684 7255 +1 800 494 3119
Holden Web LLC/Ltd http://www.holdenweb.com
Skype: holdenweb http://holdenweb.blogspot.com
Recent Ramblings http://del.icio.us/steve.holden
More information about the Python-list