Saul Spatz wrote: > Now I have another question. If dunder methods are looked up only in the > class, not the instance, why did defining __nonzero__ the way I did work? > Shouldn't I have had to define it with a def? Is __nonzero__ a special > case?
Unfortunately the situation is a bit more complex. Classic classes (like Tkinter.Frame) behave differently from newstyle classes (subclasses of object): >>> def nz(): ... print "nonzero" ... return 0 ... >>> class Classic: pass ... >>> c = Classic() >>> c.__nonzero__ = nz >>> not c nonzero True >>> class New(object): pass ... >>> n = New() >>> n.__nonzero__ = nz >>> not n False So Steven is wrong here. > Shouldn't I have had to define it with a def? If you mean as opposed to a lambda, there is no difference between f = lambda ... and def f(...): ... other than that the last one gives you a nice name in a traceback. -- http://mail.python.org/mailman/listinfo/python-list