On Mon, Sep 19, 2011 at 10:26:30PM -0400, Roy Smith wrote: > In article <4e77eae1$0$29978$c3e8da3$54964...@news.astraweb.com>, > Steven D'Aprano <steve+comp.lang.pyt...@pearwood.info> wrote: > > > Westley Mart??nez wrote: > > > > > def __radd__(self, other): > > > return self.__add__(self, other) > > > > Which, inside a class, can be simplified to: > > > > __radd__ = __add__ > > Ooh, I could see that leading to some weird diagnostics. For example: > > class Foo: > def __add__(self, other): > raise Exception > > __radd__ = __add__ > > f1 = Foo() > print 1 + f1 > > produces: > > ./add.py > Traceback (most recent call last): > File "./add.py", line 11, in <module> > print 1 + f1 > File "./add.py", line 5, in __add__ > raise Exception > Exception > > which leaves the user wondering why __add__() was called when clearly > __radd__() should have been. The way Westley wrote it (modulo fixing > the __add__() call signature) produces: > > ./add.py > Traceback (most recent call last): > File "./add.py", line 11, in <module> > print 1 + f1 > File "./add.py", line 8, in __radd__ > return self.__add__(other) > File "./add.py", line 5, in __add__ > raise Exception > Exception > > which at least is a stack trace that shows that __radd__() was called.
Calling __radd__ = __add__ simply creates a reference to __add__ named __radd__, it doesn't create a new method. -- http://mail.python.org/mailman/listinfo/python-list
