On Thu, Apr 11, 2013 at 8:41 PM, w qj <after19...@gmail.com> wrote: > I found this under Windows Python3 >>>> l="http://f/"; >>>> l[-1] is not '/' > False >>>> > > and this under Linux Python3 >>>> l = "http://ff.f/"; >>>> l[-1] > '/' >>>> l[-1] is not '/' > True > > It's Looks like a python bug?
No, this is not. The 'is' and 'is not' tests in Python are for checking the identities of Python objects - a string, a single character, a single number, everything is an object. So for example: >>> a=1 >>> b=1 >>> a is b True >>> id(a) == id(b) True When you perform the check, 'a is b', you are actually checking id(a) == id(b). In this case, since I am really referring to the same object, 1 with two different bindings - the identifier is the same. In your case, the check 'failed' on Windows and 'passed' on Linux, is because in one case, the identifiers were the same, and in another case it wasn't. So, when are identifiers same and when not? That depends on the type of object - mutable or immutable. You may want to read up on Python's data model to learn more about this. Also, more on "string interning" here. [1] [1] http://stackoverflow.com/questions/15541404/python-string-interning HTH, Amit. -- http://amitsaha.github.com/ _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
