On Mon, Oct 5, 2009 at 9:13 PM, Luke Paireepinart <rabidpoob...@gmail.com> wrote:
> Actually, I just realized that "not" has higher precedence than "==" so this > is really checking if (not n) is equal to 0, not if (n == 0) is (not) True. No, "not" is lower precedence than "==". See http://docs.python.org/reference/expressions.html#summary > Anyone have some counter-examples to n != 0 being the same as "not n == 0"? Well, you can create a pathological class where they are different: In [17]: class funky(object): ....: def __eq__(self, other): ....: return True ....: def __ne__(self, other): ....: return True In [18]: f = funky() In [19]: f != 0 Out[19]: True In [20]: f == 0 Out[20]: True In [21]: not f == 0 Out[21]: False For a less contrived example, if n is a numpy array, n==0 is also a numpy array but (not n != 0) gives an error: In [1]: from numpy import * In [2]: a = array( [ 0, 10, 20, 30, 40 ] ) In [3]: a== 0 Out[3]: array([ True, False, False, False, False], dtype=bool) In [5]: not a!= 0 --------------------------------------------------------------------------- ValueError Traceback (most recent call last) C:\Project\MangoLib\<ipython console> in <module>() ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() Kent _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
