At 01:59 PM 3/9/2008 -0800, Guido van Rossum wrote: >Do we have much of a use case for this?
I've often had APIs that take a callback that promise to only invoke the callback once, even if it's added more than once. And I've used dicts, lists, and sets for same. I did not, however, need the equality of bound methods to be based on object value equality, just value identity. ...at least until recently, anyway. I do have one library that wants to have equality-based comparison of im_self. What I ended up doing is writing code that tests what the current Python interpreter is doing, and if necessary implements a special method type, just for purposes of working around the absence of im_self equality testing. However, it's a pretty specialized case, and if I didn't have to support older Python versions I'd just use partial() -- assuming that partial() supports hashing and equality comparisons, that is, which I haven't checked. I imagine hashing a partial() might be at least as tricky as getting bound methods "right". :) >That said, if there's a use case, I agree that it would be okay with >basing the equality of x.foo and y.foo on whether x and y are the same >object, not on whether x==y (consider 0 .__add__ == 0.0 .__add__). +1 for making two bound methods m1 and m2 equal if and only if "m1.im_self is m2.im_self and m1.im_func==m2.im_func", and making the hash based on im_func and id(im_self). I don't think that the im_func comparison should be identity-based by default, however. (The im_func could be another bound method, for example.) _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
