Bugs item #1694663, was opened at 2007-04-05 01:44 Message generated for change (Comment added) made by zseil You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1694663&group_id=5470
Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: None Group: Python 2.5 Status: Open Resolution: None Priority: 3 Private: No Submitted By: Terry J. Reedy (tjreedy) Assigned to: Raymond Hettinger (rhettinger) Summary: Overloading int.__pow__ does not work Initial Comment: >From c.l.p: in response to glitch report, 2nd person showed that it is >specific to __pow__ >>> class MyInt(int): ... __sub__ = int.__add__ # similar lines for 9 other methods omitted ... __or__ = int.__add__ ... __pow__ = int.__add__ ... >>> i = MyInt(42) >>> i + 3 45 >>> i - 3 45 # similar outputs omitted >>> i | 3 45 >>> i ** 3 74088 Another person (3rd) confirmed presence in 2.5 Python 2.5 (r25:51908, Jan 21 2007, 03:10:25) [GCC 3.4.6 20060404 (Red Hat 3.4.6-3)] ---------------------------------------------------------------------- >Comment By: Ziga Seilnacht (zseil) Date: 2007-04-07 01:27 Message: Logged In: YES user_id=1326842 Originator: NO Hi Raymond, The problem is not in conversion functions, but in slot inheritance. If you run the example under a debugger you can see that MyInt->tp_as_number->nb_power == int->->tp_as_number->nb_power. This happens because update_one_slot() doesn't fall back to the generic slot function if a SlotWrapper in type's dict has a different conversion function or if it comes from an unrelated type. The patch simply falls back to the generic slot function in this case. ---------------------------------------------------------------------- Comment By: Raymond Hettinger (rhettinger) Date: 2007-04-05 06:54 Message: Logged In: YES user_id=80475 Originator: NO I'll take a look at your patch. The root problem is that the wrapper functions will return NULL if they are fed the wrong number of arguments (i.e. the int.__add__ wrapper expects exactly two arguments but the ** call provides three) -- you will see a similar result if int.__neg__ or int.__invert__ are assigned to __add__. It looks like an upstream step is seeing the NULL and deciding that it needs to look to skip the given method call and instead try the base the class. Am lowering the priority because there is no good use case for deliberate argument mismatches in the override. Am leaving the bug open because we want the appropriate error message to surface. ---------------------------------------------------------------------- Comment By: Ziga Seilnacht (zseil) Date: 2007-04-05 03:47 Message: Logged In: YES user_id=1326842 Originator: NO Here is a patch (with tests) that should fix this. There was another problem when the slot wrapper came from a different type: >>> class MyInt(int): ... __mul__ = float.__add__ ... >>> MyInt(3) * 3 9 This now raises a TypeError. File Added: mixing_slots.diff ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1694663&group_id=5470 _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
