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67 lines
2.3 KiB
67 lines
2.3 KiB
4 months ago
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:mod:`copy_reg` --- Register :mod:`pickle` support functions
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============================================================
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.. module:: copy_reg
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:synopsis: Register pickle support functions.
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.. note::
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The :mod:`copy_reg` module has been renamed to :mod:`copyreg` in Python 3.
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The :term:`2to3` tool will automatically adapt imports when converting your
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sources to Python 3.
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.. index::
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module: pickle
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module: cPickle
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module: copy
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The :mod:`copy_reg` module offers a way to define functions used while pickling
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specific objects. The :mod:`pickle`, :mod:`cPickle`, and :mod:`copy` modules
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use those functions when pickling/copying those objects. The module provides
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configuration information about object constructors which are not classes.
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Such constructors may be factory functions or class instances.
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.. function:: constructor(object)
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Declares *object* to be a valid constructor. If *object* is not callable (and
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hence not valid as a constructor), raises :exc:`TypeError`.
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.. function:: pickle(type, function[, constructor])
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Declares that *function* should be used as a "reduction" function for objects of
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type *type*; *type* must not be a "classic" class object. (Classic classes are
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handled differently; see the documentation for the :mod:`pickle` module for
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details.) *function* should return either a string or a tuple containing two or
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three elements.
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The optional *constructor* parameter, if provided, is a callable object which
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can be used to reconstruct the object when called with the tuple of arguments
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returned by *function* at pickling time. :exc:`TypeError` will be raised if
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*object* is a class or *constructor* is not callable.
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See the :mod:`pickle` module for more details on the interface expected of
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*function* and *constructor*.
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Example
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-------
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The example below would like to show how to register a pickle function and how
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it will be used:
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>>> import copy_reg, copy, pickle
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>>> class C(object):
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... def __init__(self, a):
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... self.a = a
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...
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>>> def pickle_c(c):
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... print("pickling a C instance...")
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... return C, (c.a,)
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...
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>>> copy_reg.pickle(C, pickle_c)
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>>> c = C(1)
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>>> d = copy.copy(c)
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pickling a C instance...
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>>> p = pickle.dumps(c)
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pickling a C instance...
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