This module provides generic (shallow and deep) copying operations.
Interface summary:
import copy x = copy.copy(y) # make a shallow copy of y x = copy.deepcopy(y) # make a deep copy of y
The difference between shallow and deep copying is only relevant for compound objects (objects that contain other objects, like lists or class instances):
Two problems often exist with deep copy operations that don't exist with shallow copy operations:
The deepcopy() function avoids these problems by:
This version does not copy types like module, class, function, method, stack trace, stack frame, file, socket, window, array, or any similar types.
Classes can use the same interfaces to control copying that they use
to control pickling: they can define methods called
__getinitargs__(), __getstate__() and
__setstate__(). See the description of module
pickle
In order for a class to define its own copy implementation, it can
define special methods __copy__() and
__deepcopy__(). The former is called to implement the
shallow copy operation; no additional arguments are passed. The
latter is called to implement the deep copy operation; it is passed
one argument, the memo dictionary. If the __deepcopy__()
implementation needs to make a deep copy of a component, it should
call the deepcopy() function with the component as first
argument and the memo dictionary as second argument.
See Also: