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66 lines
2.2 KiB
66 lines
2.2 KiB
4 months ago
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:mod:`copyreg` --- Register :mod:`pickle` support functions
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===========================================================
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.. module:: copyreg
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:synopsis: Register pickle support functions.
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**Source code:** :source:`Lib/copyreg.py`
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.. index::
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module: pickle
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module: copy
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--------------
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The :mod:`copyreg` module offers a way to define functions used while pickling
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specific objects. The :mod:`pickle` and :mod:`copy` modules use those functions
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when pickling/copying those objects. The module provides configuration
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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=None)
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Declares that *function* should be used as a "reduction" function for objects
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of type *type*. *function* should return either a string or a tuple
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containing two or 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
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expected of *function* and *constructor*. Note that the
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:attr:`~pickle.Pickler.dispatch_table` attribute of a pickler
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object or subclass of :class:`pickle.Pickler` can also be used for
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declaring reduction functions.
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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 copyreg, copy, pickle
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>>> class C:
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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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>>> copyreg.pickle(C, pickle_c)
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>>> c = C(1)
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>>> d = copy.copy(c) # doctest: +SKIP
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pickling a C instance...
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>>> p = pickle.dumps(c) # doctest: +SKIP
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pickling a C instance...
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