It's just like in algebra. You evaluate exponents before the - which, after all, is just another way to write -1, or times-negative-one. However, a variable with a negative value is not the same as a value that is being multiplied by a negative.
-3 ** 2 = (-1)(3)^(2) in algebraic terms. Exponents first, then multiplication. However, x ** 2 = (x)^(2) = (-3)^(2) regardless of the value of x which, in this case, is -3. When you multiply a negative by itself, you get a positive. In short, the ** operator appears to have a higher precedence than the - operator, based on your results. On Sun, Nov 29, 2009 at 6:39 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? > > > > -- > http://mail.python.org/mailman/listinfo/python-list >
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