On Fri, 27 Nov 2009 23:09:06 -0800, moijes12 wrote:
> Hi
>
> I know the value -0 is quite meaningless and makes little sense.
Actually, when it comes to floating point values, it is very useful to be
able to distinguish between -0 and +0.
> But I
> was just fiddling.I am unable to figure out the below result
>
>
>>>> -0 and True
> 0 ----------> (Why is this 0 and not say True or False)
You need to know two things about Python:
(1) All values can be interpreted in a boolean context:
if None:
print "this will never be printed"
else:
print "this is always printed"
False values include: None, 0, 0.0, "", [], {} and of course False.
True values include nearly everything else.
(2) `and` and `or` are short-cut operators. They return the first
argument which unambiguously defines the result:
X and Y => X if X is a false value, and Y if X is a true value.
X or Y => X if X is a true value, and Y if X is a false value.
Why do `and` and `or` return objects other than True and False? This is
especially useful when using `or` in situations like this:
process(main_list or fallback_list)
which will process the first list of the two which is not empty.
--
Steven
--
http://mail.python.org/mailman/listinfo/python-list
