cpython/Lib/copy_reg.py

"""Helper to provide extensibility for pickle/cPickle.

This is only useful to add pickle support for extension types defined in
C, not for instances of user-defined classes.
"""

from types import ClassType as _ClassType

dispatch_table = {}
safe_constructors = {}

def pickle(ob_type, pickle_function, constructor_ob=None):
    if type(ob_type) is _ClassType:
        raise TypeError("copy_reg is not intended for use with classes")

    if not callable(pickle_function):
        raise TypeError("reduction functions must be callable")
    dispatch_table[ob_type] = pickle_function

    if constructor_ob is not None:
        constructor(constructor_ob)

def constructor(object):
    if not callable(object):
        raise TypeError("constructors must be callable")
    safe_constructors[object] = 1

# Example: provide pickling support for complex numbers.

def pickle_complex(c):
    return complex, (c.real, c.imag)

pickle(type(1j), pickle_complex, complex)