What did I put into the dict visit passed to my __deepcopy__ custom function?

Question

I need to define my own deepcopy function for one of my classes. The documentation says that a __deepcopy__()note dictionary is passed to the function to track which objects are already copied to avoid getting into the recursive object. However, he does not say what to invest in a dictionary. Am I putting objects in objects or object identifiers? How do you use it? I cannot find any site that explains this, with the exception of this book, which states that it should not be used except to transfer it to other calls __deepcopy__.

thank

Answer 1

To match the inline behavior copy.deepcopy, you must use the idobject as a key.

More details:

Although you often manage to avoid using another key scheme (for example, the object itself, if it hashable), if you agree, you can still run into problems. Often __deepcopy__implemented by calling copy.deepcopyfor some contained attributes. If you add elements directly to memo, you must be sure that the keys will not collide with the elements added copy.deepcopy, which adds the keys generated idthat are integers.

So, if you use a different key scheme, for example, using objects directly as keys, you can never add whole objects.

:

id .

Answer 2

, @Jon-Eric:

, http://www.doughellmann.com/PyMOTW/copy/, , self , . , (self), , , , memo[self].