On Apr 10, 5:28 pm, Laszlo Nagy <gand...@shopzeus.com> wrote: > > class Uno: > > a=1 > > def m(): > > print "mouse" > > > Say that I have this "silly" class. > > > While I can then write > > > print Uno.a > > > I cannot write > > Uno.m() > > > I get the following error message: > > > TypeError: m() takes no arguments (1 given) > > As a workaround, use this pattern: > > >>> class Uno(object): > ... @classmethod > ... def m(cls): > ... print "mouse" > ... > >>> Uno.m() > mouse > > > Since I have not created any instances of Uno, there is no self > > object, and I do not understand what object is supplied to the > > function call. > > The method is not actually called, so nothing is supplied. The error is > raised when it turns out that the number of actual parameters and the > number of formal parameters are different. > > This is how you call a method: > > #1. you try to call Uno.m() - the 'm' method object is found and taken > #2. argument values are evaluated and taken (in your example, there are > no arguments) > #3. an extra argument is inserted in front of the argument list. This > parameter is the object you where calling the method on. In this case, > it is the 'Uno' class. > #4. actual arguments are assigned to formal parameters. If this fails > for some reason, an exception is raised. In your case - the number of > actual parameters is one, the number of formal parameters is zero. This > is why you get an exception. > #5. If actual and formal parameters are matched, then the implicit self > parameter is checked. If you call a method, then it must be an instance > of the class being called (or an instanc of its subclass). For > classmethods, it must be the same class (or a subclass of it). > #6. Function body executed, value returned > > The implicit parameter (the instance, or for classmethods, the class) is > ALWAYS added. So if you change your code: > > class Uno: > def m(self): > pass > > Then you won't get an exception in #4. But you will in #5, because > instance methods must be called on an instance, not on a class. You can > create a classmethod (e.g. with the @classmethod decorator) as shown > above, and it will work. > > > Could anybody explain what argument is being supplied to the method? > > Is ther any workaround to call the m function? > > > Thank you > >
Hi Laszlo, It's perfectly clear. Thank you very much -- http://mail.python.org/mailman/listinfo/python-list
