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