copyreg
— Register pickle
support functions¶
Source code: Lib/copyreg.py
The copyreg
module offers a way to define functions 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_ob=None)¶
Declares that function should be used as a „reduction” function for objects of type type. function must return either a string or a tuple containing between two and six elements. See the
dispatch_table
for more details on the interface of function.The constructor_ob parameter is a legacy feature and is now ignored, but if passed it must be a callable.
Note that the
dispatch_table
attribute of a pickler object or subclass ofpickle.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:
... 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...