| 1 | """Helper to provide extensibility for pickle/cPickle.
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| 2 |
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| 3 | This is only useful to add pickle support for extension types defined in
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| 4 | C, not for instances of user-defined classes.
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| 5 | """
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| 6 |
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| 7 | from types import ClassType as _ClassType
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| 8 |
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| 9 | __all__ = ["pickle", "constructor",
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| 10 | "add_extension", "remove_extension", "clear_extension_cache"]
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| 11 |
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| 12 | dispatch_table = {}
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| 13 |
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| 14 | def pickle(ob_type, pickle_function, constructor_ob=None):
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| 15 | if type(ob_type) is _ClassType:
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| 16 | raise TypeError("copy_reg is not intended for use with classes")
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| 17 |
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| 18 | if not hasattr(pickle_function, '__call__'):
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| 19 | raise TypeError("reduction functions must be callable")
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| 20 | dispatch_table[ob_type] = pickle_function
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| 21 |
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| 22 | # The constructor_ob function is a vestige of safe for unpickling.
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| 23 | # There is no reason for the caller to pass it anymore.
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| 24 | if constructor_ob is not None:
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| 25 | constructor(constructor_ob)
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| 26 |
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| 27 | def constructor(object):
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| 28 | if not hasattr(object, '__call__'):
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| 29 | raise TypeError("constructors must be callable")
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| 30 |
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| 31 | # Example: provide pickling support for complex numbers.
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| 32 |
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| 33 | try:
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| 34 | complex
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| 35 | except NameError:
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| 36 | pass
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| 37 | else:
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| 38 |
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| 39 | def pickle_complex(c):
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| 40 | return complex, (c.real, c.imag)
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| 41 |
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| 42 | pickle(complex, pickle_complex, complex)
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| 43 |
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| 44 | # Support for pickling new-style objects
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| 45 |
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| 46 | def _reconstructor(cls, base, state):
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| 47 | if base is object:
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| 48 | obj = object.__new__(cls)
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| 49 | else:
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| 50 | obj = base.__new__(cls, state)
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| 51 | if base.__init__ != object.__init__:
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| 52 | base.__init__(obj, state)
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| 53 | return obj
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| 54 |
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| 55 | _HEAPTYPE = 1<<9
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| 56 |
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| 57 | # Python code for object.__reduce_ex__ for protocols 0 and 1
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| 58 |
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| 59 | def _reduce_ex(self, proto):
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| 60 | assert proto < 2
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| 61 | for base in self.__class__.__mro__:
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| 62 | if hasattr(base, '__flags__') and not base.__flags__ & _HEAPTYPE:
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| 63 | break
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| 64 | else:
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| 65 | base = object # not really reachable
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| 66 | if base is object:
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| 67 | state = None
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| 68 | else:
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| 69 | if base is self.__class__:
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| 70 | raise TypeError, "can't pickle %s objects" % base.__name__
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| 71 | state = base(self)
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| 72 | args = (self.__class__, base, state)
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| 73 | try:
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| 74 | getstate = self.__getstate__
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| 75 | except AttributeError:
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| 76 | if getattr(self, "__slots__", None):
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| 77 | raise TypeError("a class that defines __slots__ without "
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| 78 | "defining __getstate__ cannot be pickled")
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| 79 | try:
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| 80 | dict = self.__dict__
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| 81 | except AttributeError:
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| 82 | dict = None
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| 83 | else:
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| 84 | dict = getstate()
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| 85 | if dict:
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| 86 | return _reconstructor, args, dict
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| 87 | else:
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| 88 | return _reconstructor, args
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| 89 |
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| 90 | # Helper for __reduce_ex__ protocol 2
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| 91 |
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| 92 | def __newobj__(cls, *args):
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| 93 | return cls.__new__(cls, *args)
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| 94 |
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| 95 | def _slotnames(cls):
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| 96 | """Return a list of slot names for a given class.
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| 97 |
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| 98 | This needs to find slots defined by the class and its bases, so we
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| 99 | can't simply return the __slots__ attribute. We must walk down
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| 100 | the Method Resolution Order and concatenate the __slots__ of each
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| 101 | class found there. (This assumes classes don't modify their
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| 102 | __slots__ attribute to misrepresent their slots after the class is
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| 103 | defined.)
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| 104 | """
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| 105 |
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| 106 | # Get the value from a cache in the class if possible
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| 107 | names = cls.__dict__.get("__slotnames__")
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| 108 | if names is not None:
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| 109 | return names
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| 110 |
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| 111 | # Not cached -- calculate the value
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| 112 | names = []
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| 113 | if not hasattr(cls, "__slots__"):
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| 114 | # This class has no slots
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| 115 | pass
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| 116 | else:
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| 117 | # Slots found -- gather slot names from all base classes
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| 118 | for c in cls.__mro__:
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| 119 | if "__slots__" in c.__dict__:
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| 120 | slots = c.__dict__['__slots__']
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| 121 | # if class has a single slot, it can be given as a string
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| 122 | if isinstance(slots, basestring):
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| 123 | slots = (slots,)
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| 124 | for name in slots:
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| 125 | # special descriptors
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| 126 | if name in ("__dict__", "__weakref__"):
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| 127 | continue
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| 128 | # mangled names
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| 129 | elif name.startswith('__') and not name.endswith('__'):
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| 130 | names.append('_%s%s' % (c.__name__, name))
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| 131 | else:
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| 132 | names.append(name)
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| 133 |
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| 134 | # Cache the outcome in the class if at all possible
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| 135 | try:
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| 136 | cls.__slotnames__ = names
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| 137 | except:
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| 138 | pass # But don't die if we can't
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| 139 |
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| 140 | return names
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| 141 |
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| 142 | # A registry of extension codes. This is an ad-hoc compression
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| 143 | # mechanism. Whenever a global reference to <module>, <name> is about
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| 144 | # to be pickled, the (<module>, <name>) tuple is looked up here to see
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| 145 | # if it is a registered extension code for it. Extension codes are
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| 146 | # universal, so that the meaning of a pickle does not depend on
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| 147 | # context. (There are also some codes reserved for local use that
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| 148 | # don't have this restriction.) Codes are positive ints; 0 is
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| 149 | # reserved.
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| 150 |
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| 151 | _extension_registry = {} # key -> code
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| 152 | _inverted_registry = {} # code -> key
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| 153 | _extension_cache = {} # code -> object
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| 154 | # Don't ever rebind those names: cPickle grabs a reference to them when
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| 155 | # it's initialized, and won't see a rebinding.
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| 156 |
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| 157 | def add_extension(module, name, code):
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| 158 | """Register an extension code."""
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| 159 | code = int(code)
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| 160 | if not 1 <= code <= 0x7fffffff:
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| 161 | raise ValueError, "code out of range"
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| 162 | key = (module, name)
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| 163 | if (_extension_registry.get(key) == code and
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| 164 | _inverted_registry.get(code) == key):
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| 165 | return # Redundant registrations are benign
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| 166 | if key in _extension_registry:
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| 167 | raise ValueError("key %s is already registered with code %s" %
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| 168 | (key, _extension_registry[key]))
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| 169 | if code in _inverted_registry:
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| 170 | raise ValueError("code %s is already in use for key %s" %
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| 171 | (code, _inverted_registry[code]))
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| 172 | _extension_registry[key] = code
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| 173 | _inverted_registry[code] = key
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| 174 |
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| 175 | def remove_extension(module, name, code):
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| 176 | """Unregister an extension code. For testing only."""
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| 177 | key = (module, name)
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| 178 | if (_extension_registry.get(key) != code or
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| 179 | _inverted_registry.get(code) != key):
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| 180 | raise ValueError("key %s is not registered with code %s" %
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| 181 | (key, code))
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| 182 | del _extension_registry[key]
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| 183 | del _inverted_registry[code]
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| 184 | if code in _extension_cache:
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| 185 | del _extension_cache[code]
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| 186 |
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| 187 | def clear_extension_cache():
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| 188 | _extension_cache.clear()
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| 189 |
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| 190 | # Standard extension code assignments
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| 191 |
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| 192 | # Reserved ranges
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| 193 |
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| 194 | # First Last Count Purpose
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| 195 | # 1 127 127 Reserved for Python standard library
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| 196 | # 128 191 64 Reserved for Zope
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| 197 | # 192 239 48 Reserved for 3rd parties
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| 198 | # 240 255 16 Reserved for private use (will never be assigned)
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| 199 | # 256 Inf Inf Reserved for future assignment
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| 200 |
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| 201 | # Extension codes are assigned by the Python Software Foundation.
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