On Sun, Nov 29, 2009 at 4:39 PM, Esmail <ebo...@hotmail.com> wrote: > Ok, this is somewhat unexpected: > > Python 2.6.2 (release26-maint, Apr 19 2009, 01:56:41) > [GCC 4.3.3] on linux2 > Type "help", "copyright", "credits" or "license" for more information. > > >>>> -3**2 > -9 > >>>> x = -3 > >>>> x**2 > 9 >>>> > > I would have expected the same result in both cases. > > Initially I would have expected -3**2 to yield 9, but I can accept > that ** binds tighter than the unary -, but shouldn't the results > be consistent regardless if I use a literal or a variable?
_No_, because using the variable evaluates "-3" as a unit separately by itself, before the exponentiation ever occurs; it's the same as the difference between (-3)**2 and -3**2. Python is not a concatenative programming language[*]; you can't directly textually replace a variable with its value and expect to get the same result from an expression. For instance, in this case, you need to add the parentheses. Cheers, Chris -- http://blog.rebertia.com [*] http://en.wikipedia.org/wiki/Concatenative_language -- http://mail.python.org/mailman/listinfo/python-list
