12.2. copyreg — Register pickle support functions — Python 3.3.7 documentation (original) (raw)

The copyreg module offers a way to define fuctions used while pickling specific objects. The pickle and 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.

copyreg.constructor(object)¶

Declares object to be a valid constructor. If object is not callable (and hence not valid as a constructor), raises TypeError.

copyreg.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. TypeError will be raised if_object_ is a class or constructor is not callable.

See the pickle module for more details on the interface expected of function and constructor. Note that thedispatch_table attribute of a pickler object or subclass of pickle.Pickler can also be used for declaring reduction functions.

12.2.1. 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) pickling a C instance... p = pickle.dumps(c) pickling a C instance...