question about True values
steve at REMOVE.THIS.cybersource.com.au
Sat Oct 28 08:28:47 CEST 2006
On Sat, 28 Oct 2006 03:13:42 +0100, Steve Holden wrote:
>> 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".
Python bools really are subclassed from ints:
>>> issubclass(bool, int)
They are ints wearing a Boolean hat. This was a controversial compromise.
>> >>> (1 > 0) < 1
>> >>> 1 > 0 < 1
>> >>> 1 > (0 < 1)
>> >>> 10 > (0 < 1)
> I have no idea what you think that you are demonstrating here.
Run through the expressions by hand:
(1 > 0) < 1
True < 1
The mere fact that you can compare bools with ints demonstrates that
Python bools aren't "real" Booleans.
>> 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
Cliff is making a point about semantics, and he's absolutely correct about
it, although it is irrelevant since we're talking about two-value logic
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