mirror of
https://github.com/python/cpython.git
synced 2024-11-25 19:03:49 +08:00
428 lines
11 KiB
Python
428 lines
11 KiB
Python
"""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 in 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
|
|
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_atomic(x):
|
|
return x
|
|
d[types.NoneType] = _copy_atomic
|
|
d[types.IntType] = _copy_atomic
|
|
d[types.LongType] = _copy_atomic
|
|
d[types.FloatType] = _copy_atomic
|
|
d[types.BooleanType] = _copy_atomic
|
|
try:
|
|
d[types.ComplexType] = _copy_atomic
|
|
except AttributeError:
|
|
pass
|
|
d[types.StringType] = _copy_atomic
|
|
try:
|
|
d[types.UnicodeType] = _copy_atomic
|
|
except AttributeError:
|
|
pass
|
|
try:
|
|
d[types.CodeType] = _copy_atomic
|
|
except AttributeError:
|
|
pass
|
|
d[types.TypeType] = _copy_atomic
|
|
d[types.XRangeType] = _copy_atomic
|
|
d[types.ClassType] = _copy_atomic
|
|
|
|
def _copy_list(x):
|
|
return x[:]
|
|
d[types.ListType] = _copy_list
|
|
|
|
def _copy_tuple(x):
|
|
return x[:]
|
|
d[types.TupleType] = _copy_tuple
|
|
|
|
def _copy_dict(x):
|
|
return x.copy()
|
|
d[types.DictionaryType] = _copy_dict
|
|
if PyStringMap is not None:
|
|
d[PyStringMap] = _copy_dict
|
|
|
|
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[types.NoneType] = _deepcopy_atomic
|
|
d[types.IntType] = _deepcopy_atomic
|
|
d[types.LongType] = _deepcopy_atomic
|
|
d[types.FloatType] = _deepcopy_atomic
|
|
d[types.BooleanType] = _deepcopy_atomic
|
|
try:
|
|
d[types.ComplexType] = _deepcopy_atomic
|
|
except AttributeError:
|
|
pass
|
|
d[types.StringType] = _deepcopy_atomic
|
|
try:
|
|
d[types.UnicodeType] = _deepcopy_atomic
|
|
except AttributeError:
|
|
pass
|
|
try:
|
|
d[types.CodeType] = _deepcopy_atomic
|
|
except AttributeError:
|
|
pass
|
|
d[types.TypeType] = _deepcopy_atomic
|
|
d[types.XRangeType] = _deepcopy_atomic
|
|
d[types.ClassType] = _deepcopy_atomic
|
|
|
|
def _deepcopy_list(x, memo):
|
|
y = []
|
|
memo[id(x)] = y
|
|
for a in x:
|
|
y.append(deepcopy(a, memo))
|
|
return y
|
|
d[types.ListType] = _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[types.TupleType] = _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[types.DictionaryType] = _deepcopy_dict
|
|
if 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 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 = {}
|
|
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)
|
|
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()
|