copyreg module offers a way to define functions used while pickling
specific objects. The
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.
Declares object to be a valid constructor. If object is not callable (and hence not valid as a constructor), raises
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.
TypeErrorwill be raised if object is a class or constructor is not callable.
picklemodule for more details on the interface expected of function and constructor. Note that the
dispatch_tableattribute of a pickler object or subclass of
pickle.Picklercan 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(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...