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File name : copy.py

Content :"""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 for compound objects (objects that contain other objects, like lists or class 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 exist with 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, nor any similar types. Classes can use the same interfaces to control copying that they use to control pickling: they can define methods called __getinitargs__(), __getstate__() and __setstate__(). See the documentation for module "pickle" for information on these methods. """ import types import weakref from copy_reg import dispatch_table class Error(Exception): pass error = Error # backward compatibility try: from org.python.core import PyStringMap except 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 x for t in (type(None), int, long, float, bool, str, tuple, frozenset, type, xrange, types.ClassType, types.BuiltinFunctionType, type(Ellipsis), types.FunctionType, weakref.ref): d[t] = _copy_immutable for 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 y d[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 x d[type(None)] = _deepcopy_atomic d[type(Ellipsis)] = _deepcopy_atomic d[int] = _deepcopy_atomic d[long] = _deepcopy_atomic d[float] = _deepcopy_atomic d[bool] = _deepcopy_atomic try: d[complex] = _deepcopy_atomic except NameError: pass d[str] = _deepcopy_atomic try: d[unicode] = _deepcopy_atomic except NameError: pass try: d[types.CodeType] = _deepcopy_atomic except AttributeError: pass d[type] = _deepcopy_atomic d[xrange] = _deepcopy_atomic d[types.ClassType] = _deepcopy_atomic d[types.BuiltinFunctionType] = _deepcopy_atomic d[types.FunctionType] = _deepcopy_atomic d[weakref.ref] = _deepcopy_atomic def _deepcopy_list(x, memo): y = [] memo[id(x)] = y for a in x: y.append(deepcopy(a, memo)) return y d[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 y d[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 y d[dict] = _deepcopy_dict if PyStringMap is not None: d[PyStringMap] = _deepcopy_dict def _deepcopy_method(x, memo): # Copy instance methods return type(x)(x.im_func, deepcopy(x.im_self, memo), x.im_class) _deepcopy_dispatch[types.MethodType] = _deepcopy_method 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 y d[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 = None 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 state is not None: 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) 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 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) class odict(dict): def __init__(self, d = {}): self.a = 99 dict.__init__(self, d) def __setitem__(self, k, i): dict.__setitem__(self, k, i) self.a o = odict({"A" : "B"}) x = deepcopy(o) print(o, x) if __name__ == '__main__': _test()

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