11.4.2 Copying Objects

The module copy exports two functions: copy() and deepcopy(). The copy() function returns a ``shallow'' copy of an object; deepcopy() returns a ``deep'' copy. The difference between shallow and deep copying is only relevant for compound objects (objects that contain other objects, like lists or class instances):

• A shallow copy constructs a new compound object and then (to the extent possible) inserts the same objects into in that the original contains.
• A deep copy constructs a new compound object and then, recursively, inserts copies into it of the objects found in the original.

Both functions have the same restrictions and use the same protocols as pickle -- user-defined classes can control how they are copied by providing methods named __getinitargs__(), __getstate__() and __setstate__().