copyreg — Registerpickle support functions¶

Source code:Lib/copyreg.py

Thecopyreg module offers a way to define functions used while picklingspecific objects. Thepickle andcopy modules use those functionswhen pickling/copying those objects. The module provides configurationinformation about object constructors which are not classes.Such constructors may be factory functions or class instances.

copyreg.constructor(object)¶

Declaresobject to be a valid constructor. Ifobject is not callable (andhence not valid as a constructor), raisesTypeError.

copyreg.pickle(type,function,constructor=None)¶

Declares thatfunction should be used as a “reduction” function for objectsof typetype.function should return either a string or a tuplecontaining two or three elements.

The optionalconstructor parameter, if provided, is a callable object whichcan be used to reconstruct the object when called with the tuple of argumentsreturned byfunction at pickling time.TypeError will be raised ifobject is a class orconstructor is not callable.

See thepickle module for more details on the interfaceexpected offunction andconstructor. Note that thedispatch_table attribute of a picklerobject or subclass ofpickle.Pickler can also be used fordeclaring reduction functions.

>>>importcopyreg,copy,pickle>>>classC(object):...def__init__(self,a):...self.a=a...>>>defpickle_c(c):...print("pickling a C instance...")...returnC,(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...