Alexander Belopolsky <belopol...@users.sourceforge.net> added the comment:
On Wed, Jul 21, 2010 at 2:09 AM, Ray.Allen <rep...@bugs.python.org> wrote: .. > Does this means "a += b" is not the same as "a = a + b"? For immutable a, the two are practically the same, for mutable, they are necessarily different. This is explained in __iadd__ documentation: """ These methods are called to implement the augmented arithmetic assignments (+=, -=, *=, /=, //=, %=, **=, <<=, >>=, &=, ^=, |=). These methods should attempt to do the operation in-place (modifying self) and return the result (which could be, but does not have to be, self). If a specific method is not defined, the augmented assignment falls back to the normal methods. For instance, to execute the statement x += y, where x is an instance of a class that has an __iadd__() method, x.__iadd__(y) is called. If x is an instance of a class that does not define a __iadd__() method, x.__add__(y) and y.__radd__(x) are considered, as with the evaluation of x + y. """ http://docs.python.org/reference/datamodel.html?#object.__iadd__ > I'd think this can be seen as a pitfall for python. No. Please see PEP 203 for the rationale. http://www.python.org/dev/peps/pep-0203/ ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue9314> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
