On 20 Mai, 22:58, [EMAIL PROTECTED] wrote: > class TaskGroup: > def __init__(self): > self.group = [] > > def addTask(self, task): > self.group.append(task) > > is this wrong? i have a program thats too big to post but should i > just do group.append in addTask?
No, you have to do self.group.append, since group isn't a local variable in the addTask method, and I doubt that you'd want addTask to make changes to any global variable called group, which is what might happen otherwise - that could be a source of potential problems, so you need to be aware of that! > reason is when later doing TaskGroup.group i get None TaskGroup.group would be referencing a class attribute called group, which is "shared" by all TaskGroup instances (and the TaskGroup class itself, of course). What you need to do is to access the instance attribute called group via each instance, and the self.group notation does exactly that: self is the reference to a particular instance (in the addTask method, it's the instance used to call the addTask method). You might wonder why Python doesn't know inside a method that group is a reference to an instance attribute of that name. The reason, somewhat simplified, is that Python only has assignments to populate namespaces (such as the contents of an instance), whereas languages which employ declarations (such as Java) would have you list the instance attributes up front. In these other languages, the compiler/ interpreter would know that you're executing a method belonging to an instance of a particular class, and it would also know what names to expect as references to class and instance attributes. Anyway, I hope this makes more sense now than it did a few moments ago. :-) Paul -- http://mail.python.org/mailman/listinfo/python-list
