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 > 4 > >>> bool(True-1) > False > >>> bool(True-2) > True > >>> (10 > 5) + (10 < 5) > 1 > > 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) > >>> type(10>5) <type 'bool'> >>> 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 > False > >>> 1 > 0 < 1 > True > >>> 1 > (0 < 1) > False > >>> 10 > (0 < 1) > True > 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" ... else: ... print "Sorry: of course you are perfectly correct" ... You don't know what you are talking about >>> regards Steve -- 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 -- http://mail.python.org/mailman/listinfo/python-list
