Hi, folks, First, the obligatory cheerleading -- then, my questions...
I love Python! I am only an occasional programmer. Still, the logic of the language is clear enough that I can retain pretty much all that I have learned from one infrequent programming session to the next. That's quite an accomplishment for a language this powerful. Also, I'm finally beginning to grasp OOP. I could never quite get the hang of it in C++ or Java. Recently, I discovered __getitem__ and pickle. Oh, yeah. Anyway, my present problem is that I want to make copies of instances of my own custom classes. I'm having a little trouble understanding the process. Not that I think that it matters -- but in case it does, I'll tell you that I'm running Python 2.3.4 on a Win32 machine. I started naively, thinking that I could just call copy.deepcopy() and be done with it. After getting a TypeError from the interpreter, I read the deepcopy docs and discovered that I need to implement a __deepcopy__ method in my class. But the docs are a bit vague here. What exactly should this __deepcopy__ do? I tried looking for examples of __deepcopy__ code on the Net, but I'm not quite understanding what I'm finding there. I guess that I'm getting deeper into the guts of Python than I planned. AFAIK, I'm supposed to add a "def __deepcopy__(self, memo):" to my class definition. This will get called when I invoke copy.deepcopy(myObject). The object to be copied is self, I presume. What exactly is memo? The docs say that it's a dictionary which "keeps track of what has already been copied." Somewhere I remember reading that the namespace of an object is a dictionary. So is memo identical to the dictionary of the new object that I'm trying to create? What exactly do I add to memo? I think that I should make shallow copies of methods, but deep copies of data structures (the contents of which I'm likely to change). Do I iterate through and copy the items in dir(self)? Do I update memo manually, or does passing memo into copy() or deepcopy() automatically update memo's contents? Are there any items that I *shouldn't* copy from self to memo? Should __deepcopy__ return memo? Sorry for all the confusion -- and thanks for your help! -- Rainforest laid low. "Wake up and smell the ozone," Says man with chainsaw. John J. Ladasky Jr., Ph.D. -- http://mail.python.org/mailman/listinfo/python-list
