1:mod:`copy_reg` --- Register :mod:`pickle` support functions 2============================================================ 3 4.. module:: copy_reg 5 :synopsis: Register pickle support functions. 6 7.. note:: 8 The :mod:`copy_reg` module has been renamed to :mod:`copyreg` in Python 3. 9 The :term:`2to3` tool will automatically adapt imports when converting your 10 sources to Python 3. 11 12.. index:: 13 module: pickle 14 module: cPickle 15 module: copy 16 17The :mod:`copy_reg` module offers a way to define functions used while pickling 18specific objects. The :mod:`pickle`, :mod:`cPickle`, and :mod:`copy` modules 19use those functions when pickling/copying those objects. The module provides 20configuration information about object constructors which are not classes. 21Such constructors may be factory functions or class instances. 22 23 24.. function:: constructor(object) 25 26 Declares *object* to be a valid constructor. If *object* is not callable (and 27 hence not valid as a constructor), raises :exc:`TypeError`. 28 29 30.. function:: pickle(type, function[, constructor]) 31 32 Declares that *function* should be used as a "reduction" function for objects of 33 type *type*; *type* must not be a "classic" class object. (Classic classes are 34 handled differently; see the documentation for the :mod:`pickle` module for 35 details.) *function* should return either a string or a tuple containing two or 36 three elements. 37 38 The optional *constructor* parameter, if provided, is a callable object which 39 can be used to reconstruct the object when called with the tuple of arguments 40 returned by *function* at pickling time. :exc:`TypeError` will be raised if 41 *object* is a class or *constructor* is not callable. 42 43 See the :mod:`pickle` module for more details on the interface expected of 44 *function* and *constructor*. 45 46Example 47------- 48 49The example below would like to show how to register a pickle function and how 50it will be used: 51 52 >>> import copy_reg, copy, pickle 53 >>> class C(object): 54 ... def __init__(self, a): 55 ... self.a = a 56 ... 57 >>> def pickle_c(c): 58 ... print("pickling a C instance...") 59 ... return C, (c.a,) 60 ... 61 >>> copy_reg.pickle(C, pickle_c) 62 >>> c = C(1) 63 >>> d = copy.copy(c) 64 pickling a C instance... 65 >>> p = pickle.dumps(c) 66 pickling a C instance... 67