Doc/library/copyreg.rst
!copyreg --- Register :mod:!pickle support functions.. module:: copyreg :synopsis: Register pickle support functions.
Source code: :source:Lib/copyreg.py
.. index:: pair: module; pickle pair: module; copy
The :mod:!copyreg module offers a way to define functions used while pickling
specific objects. The :mod:pickle and :mod:copy modules use those functions
when pickling/copying those objects. The module provides configuration
information about object constructors which are not classes.
Such constructors may be factory functions or class instances.
.. function:: constructor(object)
Declares object to be a valid constructor. If object is not callable (and
hence not valid as a constructor), raises :exc:TypeError.
.. function:: pickle(type, function, constructor_ob=None)
Declares that function should be used as a "reduction" function for objects
of type type. function must return either a string or a tuple
containing between two and six elements. See the :attr:~pickle.Pickler.dispatch_table
for more details on the interface of function.
The constructor_ob parameter is a legacy feature and is now ignored, but if passed it must be a callable.
Note that the :attr:~pickle.Pickler.dispatch_table attribute of a pickler
object or subclass of :class:pickle.Pickler can also be used for
declaring reduction functions.
The example below would like to show how to register a pickle function and how it will be used:
import copyreg, copy, pickle class C: ... def init(self, a): ... self.a = a ... def pickle_c(c): ... print("pickling a C instance...") ... return C, (c.a,) ... copyreg.pickle(C, pickle_c) c = C(1) d = copy.copy(c) # doctest: +SKIP pickling a C instance... p = pickle.dumps(c) # doctest: +SKIP pickling a C instance...