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4b8c6eaf8b
*this* set of patches is Ka-Ping's final sweep: The attached patches update the standard library so that all modules have docstrings beginning with one-line summaries. A new docstring was added to formatter. The docstring for os.py was updated to mention nt, os2, ce in addition to posix, dos, mac.
305 lines
6.9 KiB
Python
305 lines
6.9 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 in 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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# XXX need to support copy_reg here too...
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import types
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error = 'copy.error'
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Error = error # backward compatibility
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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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try:
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copierfunction = _copy_dispatch[type(x)]
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except KeyError:
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try:
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copier = x.__copy__
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except AttributeError:
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raise error, \
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"un(shallow)copyable object of type %s" % type(x)
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y = copier()
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else:
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y = copierfunction(x)
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return y
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_copy_dispatch = d = {}
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def _copy_atomic(x):
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return x
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d[types.NoneType] = _copy_atomic
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d[types.IntType] = _copy_atomic
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d[types.LongType] = _copy_atomic
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d[types.FloatType] = _copy_atomic
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d[types.StringType] = _copy_atomic
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try:
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d[types.CodeType] = _copy_atomic
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except AttributeError:
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pass
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d[types.TypeType] = _copy_atomic
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d[types.XRangeType] = _copy_atomic
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d[types.ClassType] = _copy_atomic
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def _copy_list(x):
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return x[:]
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d[types.ListType] = _copy_list
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def _copy_tuple(x):
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return x[:]
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d[types.TupleType] = _copy_tuple
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def _copy_dict(x):
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return x.copy()
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d[types.DictionaryType] = _copy_dict
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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 = apply(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):
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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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if memo.has_key(d):
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return memo[d]
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try:
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copierfunction = _deepcopy_dispatch[type(x)]
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except KeyError:
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try:
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copier = x.__deepcopy__
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except AttributeError:
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raise error, \
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"un-deep-copyable object of type %s" % type(x)
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y = copier(memo)
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else:
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y = copierfunction(x, memo)
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memo[d] = y
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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[types.NoneType] = _deepcopy_atomic
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d[types.IntType] = _deepcopy_atomic
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d[types.LongType] = _deepcopy_atomic
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d[types.FloatType] = _deepcopy_atomic
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d[types.StringType] = _deepcopy_atomic
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d[types.CodeType] = _deepcopy_atomic
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d[types.TypeType] = _deepcopy_atomic
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d[types.XRangeType] = _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[types.ListType] = _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[types.TupleType] = _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 in x.keys():
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y[deepcopy(key, memo)] = deepcopy(x[key], memo)
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return y
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d[types.DictionaryType] = _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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_keep_alive(args, memo)
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args = deepcopy(args, memo)
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y = apply(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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_keep_alive(state, memo)
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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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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 in state.keys():
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setattr(self, key, state[key])
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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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