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417 lines
11 KiB
Python
417 lines
11 KiB
Python
"""Generic (shallow and deep) copying operations.
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Interface summary:
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import copy
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x = copy.copy(y) # make a shallow copy of y
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x = copy.deepcopy(y) # make a deep copy of y
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For module specific errors, copy.Error is raised.
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The difference between shallow and deep copying is only relevant for
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compound objects (objects that contain other objects, like lists or
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class instances).
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- A shallow copy constructs a new compound object and then (to the
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extent possible) inserts *the same objects* into it that the
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original contains.
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- A deep copy constructs a new compound object and then, recursively,
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inserts *copies* into it of the objects found in the original.
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Two problems often exist with deep copy operations that don't exist
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with shallow copy operations:
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a) recursive objects (compound objects that, directly or indirectly,
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contain a reference to themselves) may cause a recursive loop
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b) because deep copy copies *everything* it may copy too much, e.g.
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administrative data structures that should be shared even between
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copies
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Python's deep copy operation avoids these problems by:
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a) keeping a table of objects already copied during the current
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copying pass
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b) letting user-defined classes override the copying operation or the
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set of components copied
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This version does not copy types like module, class, function, method,
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nor stack trace, stack frame, nor file, socket, window, nor array, nor
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any similar types.
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Classes can use the same interfaces to control copying that they use
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to control pickling: they can define methods called __getinitargs__(),
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__getstate__() and __setstate__(). See the documentation for module
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"pickle" for information on these methods.
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"""
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import types
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import weakref
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from copy_reg import dispatch_table
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class Error(Exception):
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pass
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error = Error # backward compatibility
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try:
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from org.python.core import PyStringMap
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except ImportError:
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PyStringMap = None
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__all__ = ["Error", "copy", "deepcopy"]
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def copy(x):
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"""Shallow copy operation on arbitrary Python objects.
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See the module's __doc__ string for more info.
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"""
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cls = type(x)
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copier = _copy_dispatch.get(cls)
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if copier:
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return copier(x)
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copier = getattr(cls, "__copy__", None)
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if copier:
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return copier(x)
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reductor = dispatch_table.get(cls)
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if reductor:
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rv = reductor(x)
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else:
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reductor = getattr(x, "__reduce_ex__", None)
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if reductor:
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rv = reductor(2)
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else:
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reductor = getattr(x, "__reduce__", None)
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if reductor:
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rv = reductor()
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else:
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raise Error("un(shallow)copyable object of type %s" % cls)
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return _reconstruct(x, rv, 0)
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_copy_dispatch = d = {}
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def _copy_immutable(x):
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return x
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for t in (type(None), int, long, float, bool, str, tuple,
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frozenset, type, xrange, types.ClassType,
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types.BuiltinFunctionType, type(Ellipsis),
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types.FunctionType, weakref.ref):
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d[t] = _copy_immutable
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for name in ("ComplexType", "UnicodeType", "CodeType"):
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t = getattr(types, name, None)
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if t is not None:
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d[t] = _copy_immutable
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def _copy_with_constructor(x):
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return type(x)(x)
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for t in (list, dict, set):
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d[t] = _copy_with_constructor
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def _copy_with_copy_method(x):
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return x.copy()
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if PyStringMap is not None:
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d[PyStringMap] = _copy_with_copy_method
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def _copy_inst(x):
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if hasattr(x, '__copy__'):
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return x.__copy__()
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if hasattr(x, '__getinitargs__'):
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args = x.__getinitargs__()
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y = x.__class__(*args)
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else:
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y = _EmptyClass()
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y.__class__ = x.__class__
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if hasattr(x, '__getstate__'):
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state = x.__getstate__()
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else:
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state = x.__dict__
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if hasattr(y, '__setstate__'):
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y.__setstate__(state)
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else:
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y.__dict__.update(state)
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return y
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d[types.InstanceType] = _copy_inst
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del d
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def deepcopy(x, memo=None, _nil=[]):
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"""Deep copy operation on arbitrary Python objects.
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See the module's __doc__ string for more info.
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"""
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if memo is None:
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memo = {}
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d = id(x)
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y = memo.get(d, _nil)
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if y is not _nil:
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return y
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cls = type(x)
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copier = _deepcopy_dispatch.get(cls)
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if copier:
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y = copier(x, memo)
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else:
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try:
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issc = issubclass(cls, type)
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except TypeError: # cls is not a class (old Boost; see SF #502085)
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issc = 0
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if issc:
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y = _deepcopy_atomic(x, memo)
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else:
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copier = getattr(x, "__deepcopy__", None)
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if copier:
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y = copier(memo)
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else:
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reductor = dispatch_table.get(cls)
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if reductor:
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rv = reductor(x)
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else:
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reductor = getattr(x, "__reduce_ex__", None)
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if reductor:
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rv = reductor(2)
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else:
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reductor = getattr(x, "__reduce__", None)
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if reductor:
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rv = reductor()
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else:
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raise Error(
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"un(deep)copyable object of type %s" % cls)
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y = _reconstruct(x, rv, 1, memo)
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memo[d] = y
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_keep_alive(x, memo) # Make sure x lives at least as long as d
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return y
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_deepcopy_dispatch = d = {}
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def _deepcopy_atomic(x, memo):
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return x
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d[type(None)] = _deepcopy_atomic
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d[type(Ellipsis)] = _deepcopy_atomic
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d[int] = _deepcopy_atomic
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d[long] = _deepcopy_atomic
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d[float] = _deepcopy_atomic
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d[bool] = _deepcopy_atomic
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try:
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d[complex] = _deepcopy_atomic
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except NameError:
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pass
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d[str] = _deepcopy_atomic
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try:
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d[unicode] = _deepcopy_atomic
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except NameError:
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pass
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try:
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d[types.CodeType] = _deepcopy_atomic
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except AttributeError:
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pass
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d[type] = _deepcopy_atomic
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d[xrange] = _deepcopy_atomic
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d[types.ClassType] = _deepcopy_atomic
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d[types.BuiltinFunctionType] = _deepcopy_atomic
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d[types.FunctionType] = _deepcopy_atomic
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d[weakref.ref] = _deepcopy_atomic
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def _deepcopy_list(x, memo):
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y = []
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memo[id(x)] = y
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for a in x:
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y.append(deepcopy(a, memo))
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return y
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d[list] = _deepcopy_list
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def _deepcopy_tuple(x, memo):
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y = []
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for a in x:
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y.append(deepcopy(a, memo))
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d = id(x)
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try:
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return memo[d]
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except KeyError:
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pass
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for i in range(len(x)):
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if x[i] is not y[i]:
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y = tuple(y)
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break
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else:
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y = x
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memo[d] = y
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return y
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d[tuple] = _deepcopy_tuple
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def _deepcopy_dict(x, memo):
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y = {}
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memo[id(x)] = y
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for key, value in x.iteritems():
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y[deepcopy(key, memo)] = deepcopy(value, memo)
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return y
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d[dict] = _deepcopy_dict
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if PyStringMap is not None:
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d[PyStringMap] = _deepcopy_dict
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def _keep_alive(x, memo):
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"""Keeps a reference to the object x in the memo.
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Because we remember objects by their id, we have
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to assure that possibly temporary objects are kept
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alive by referencing them.
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We store a reference at the id of the memo, which should
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normally not be used unless someone tries to deepcopy
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the memo itself...
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"""
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try:
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memo[id(memo)].append(x)
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except KeyError:
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# aha, this is the first one :-)
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memo[id(memo)]=[x]
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def _deepcopy_inst(x, memo):
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if hasattr(x, '__deepcopy__'):
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return x.__deepcopy__(memo)
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if hasattr(x, '__getinitargs__'):
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args = x.__getinitargs__()
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args = deepcopy(args, memo)
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y = x.__class__(*args)
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else:
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y = _EmptyClass()
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y.__class__ = x.__class__
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memo[id(x)] = y
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if hasattr(x, '__getstate__'):
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state = x.__getstate__()
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else:
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state = x.__dict__
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state = deepcopy(state, memo)
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if hasattr(y, '__setstate__'):
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y.__setstate__(state)
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else:
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y.__dict__.update(state)
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return y
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d[types.InstanceType] = _deepcopy_inst
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def _reconstruct(x, info, deep, memo=None):
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if isinstance(info, str):
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return x
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assert isinstance(info, tuple)
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if memo is None:
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memo = {}
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n = len(info)
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assert n in (2, 3, 4, 5)
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callable, args = info[:2]
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if n > 2:
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state = info[2]
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else:
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state = {}
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if n > 3:
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listiter = info[3]
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else:
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listiter = None
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if n > 4:
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dictiter = info[4]
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else:
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dictiter = None
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if deep:
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args = deepcopy(args, memo)
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y = callable(*args)
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memo[id(x)] = y
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if listiter is not None:
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for item in listiter:
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if deep:
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item = deepcopy(item, memo)
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y.append(item)
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if dictiter is not None:
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for key, value in dictiter:
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if deep:
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key = deepcopy(key, memo)
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value = deepcopy(value, memo)
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y[key] = value
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if state:
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if deep:
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state = deepcopy(state, memo)
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if hasattr(y, '__setstate__'):
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y.__setstate__(state)
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else:
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if isinstance(state, tuple) and len(state) == 2:
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state, slotstate = state
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else:
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slotstate = None
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if state is not None:
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y.__dict__.update(state)
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if slotstate is not None:
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for key, value in slotstate.iteritems():
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setattr(y, key, value)
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return y
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del d
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del types
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# Helper for instance creation without calling __init__
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class _EmptyClass:
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pass
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def _test():
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l = [None, 1, 2L, 3.14, 'xyzzy', (1, 2L), [3.14, 'abc'],
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{'abc': 'ABC'}, (), [], {}]
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l1 = copy(l)
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print l1==l
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l1 = map(copy, l)
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print l1==l
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l1 = deepcopy(l)
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print l1==l
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class C:
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def __init__(self, arg=None):
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self.a = 1
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self.arg = arg
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if __name__ == '__main__':
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import sys
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file = sys.argv[0]
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else:
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file = __file__
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self.fp = open(file)
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self.fp.close()
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def __getstate__(self):
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return {'a': self.a, 'arg': self.arg}
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def __setstate__(self, state):
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for key, value in state.iteritems():
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setattr(self, key, value)
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def __deepcopy__(self, memo=None):
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new = self.__class__(deepcopy(self.arg, memo))
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new.a = self.a
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return new
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c = C('argument sketch')
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l.append(c)
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l2 = copy(l)
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print l == l2
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print l
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print l2
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l2 = deepcopy(l)
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print l == l2
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print l
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print l2
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l.append({l[1]: l, 'xyz': l[2]})
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l3 = copy(l)
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import repr
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print map(repr.repr, l)
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print map(repr.repr, l1)
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print map(repr.repr, l2)
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print map(repr.repr, l3)
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l3 = deepcopy(l)
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import repr
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print map(repr.repr, l)
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print map(repr.repr, l1)
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print map(repr.repr, l2)
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print map(repr.repr, l3)
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if __name__ == '__main__':
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_test()
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