:mod:copyreg --- Register :mod:pickle support functions

.. module:: copyreg :synopsis: Register pickle support functions.

Source code: :source:Lib/copyreg.py

.. index:: module: pickle 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=None)

Declares that function should be used as a "reduction" function for objects of type type. function should return either a string or a tuple containing two or three elements.

The optional constructor parameter, if provided, is a callable object which can be used to reconstruct the object when called with the tuple of arguments returned by function at pickling time. :exc:TypeError will be raised if object is a class or constructor is not callable.

See the :mod:pickle module for more details on the interface expected of function and constructor. 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.

Example

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(object): ... 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...