> ...classes don't invoke the function directly, they convert it to > an 'unbound method' object:: > > >>> class Test(object): > ... def greet(): > ... print 'Hello' > ... > >>> Test.greet > <unbound method Test.greet> > >>> Test.greet() > Traceback (most recent call last): > File "<interactive input>", line 1, in <module> > TypeError: unbound method greet() must be called with Test instance > as first argument (got nothing instead) >
I think I found the rule in the GvF tutorial, which is essentially what the error message says: ------- When an unbound user-defined method object is called, the underlying function (im_func) is called, with the restriction that the first argument must be an instance of the proper class (im_class) or of a derived class thereof. -------- So, if you call a function using the syntax TheClass.theMethod(), then you are required to use an instance object as an argument. In section 3.2 The Standard Class Hierarchy, it also says this: ------- When a user-defined method object is created by retrieving a user- defined function object from a class, its im_self attribute is None and the method object is said to be unbound. When one is created by retrieving a user-defined function object from a class via one of its instances, its im_self attribute is the instance, and the method object is said to be bound. -------- In that first sentence, is he talking about retrieving the user- defined function object from the class using the class name, e.g: MyClass.someFunc Is there some other way to retrieve a user-defined function object from a class other than using the class name or an instance? > If you really want to get to the original function, there are a couple > of options. No. Just trying to figure out how some things work. -- http://mail.python.org/mailman/listinfo/python-list
