cpython/Lib/copy.py

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"""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
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
compound objects (objects that contain other objects, like lists or
class instances).
- 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.
- 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,
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contain a reference to themselves) may cause a recursive loop
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
copies
Python's deep copy operation avoids these problems by:
a) keeping a table of objects already copied during the current
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
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
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"pickle" for information on these methods.
"""
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import types
import weakref
from copyreg import dispatch_table
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class Error(Exception):
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pass
error = Error # backward compatibility
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try:
from org.python.core import PyStringMap
except ImportError:
PyStringMap = None
__all__ = ["Error", "copy", "deepcopy"]
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def copy(x):
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"""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)
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_copy_dispatch = d = {}
def _copy_immutable(x):
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return x
for t in (type(None), int, float, bool, str, tuple,
frozenset, type, range,
Merged revisions 61834,61841-61842,61851-61853,61863-61864,61869-61870,61874,61889 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r61834 | raymond.hettinger | 2008-03-24 07:07:49 +0100 (Mon, 24 Mar 2008) | 1 line Tighten documentation for Random.triangular. ........ r61841 | raymond.hettinger | 2008-03-24 09:17:39 +0100 (Mon, 24 Mar 2008) | 1 line Issue 2460: Make Ellipsis objects copyable. ........ r61842 | georg.brandl | 2008-03-24 10:34:34 +0100 (Mon, 24 Mar 2008) | 2 lines #1700821: add a note to audioop docs about signedness of sample formats. ........ r61851 | christian.heimes | 2008-03-24 20:57:42 +0100 (Mon, 24 Mar 2008) | 1 line Added quick hack for bzr ........ r61852 | christian.heimes | 2008-03-24 20:58:17 +0100 (Mon, 24 Mar 2008) | 1 line Added quick hack for bzr ........ r61853 | amaury.forgeotdarc | 2008-03-24 22:04:10 +0100 (Mon, 24 Mar 2008) | 4 lines Issue2469: Correct a typo I introduced at r61793: compilation error with UCS4 builds. All buildbots compile with UCS2... ........ r61863 | neal.norwitz | 2008-03-25 05:17:38 +0100 (Tue, 25 Mar 2008) | 2 lines Fix a bunch of UnboundLocalErrors when the tests fail. ........ r61864 | neal.norwitz | 2008-03-25 05:18:18 +0100 (Tue, 25 Mar 2008) | 2 lines Try to fix a bunch of compiler warnings on Win64. ........ r61869 | neal.norwitz | 2008-03-25 07:35:10 +0100 (Tue, 25 Mar 2008) | 3 lines Don't try to close a non-open file. Don't let file removal cause the test to fail. ........ r61870 | neal.norwitz | 2008-03-25 08:00:39 +0100 (Tue, 25 Mar 2008) | 7 lines Try to get this test to be more stable: * disable gc during the test run because we are spawning objects and there was an exception when calling Popen.__del__ * Always set an alarm handler so the process doesn't exit if the test fails (should probably add assertions on the value of hndl_called in more places) * Using a negative time causes Linux to treat it as zero, so disable that test. ........ r61874 | gregory.p.smith | 2008-03-25 08:31:28 +0100 (Tue, 25 Mar 2008) | 2 lines Use a 32-bit unsigned int here, a long is not needed. ........ r61889 | georg.brandl | 2008-03-25 12:59:51 +0100 (Tue, 25 Mar 2008) | 2 lines Move declarations to block start. ........
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types.BuiltinFunctionType, type(Ellipsis),
types.FunctionType, weakref.ref):
d[t] = _copy_immutable
t = getattr(types, "CodeType", None)
if t is not None:
d[t] = _copy_immutable
for name in ("complex", "unicode"):
t = globals()['__builtins__'].get(name)
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):
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return x.copy()
if PyStringMap is not None:
d[PyStringMap] = _copy_with_copy_method
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del d
def deepcopy(x, memo=None, _nil=[]):
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"""Deep copy operation on arbitrary Python objects.
See the module's __doc__ string for more info.
"""
if memo is None:
memo = {}
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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:
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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)
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memo[d] = y
_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 = {}
def _deepcopy_atomic(x, memo):
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return x
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d[type(None)] = _deepcopy_atomic
Merged revisions 61834,61841-61842,61851-61853,61863-61864,61869-61870,61874,61889 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r61834 | raymond.hettinger | 2008-03-24 07:07:49 +0100 (Mon, 24 Mar 2008) | 1 line Tighten documentation for Random.triangular. ........ r61841 | raymond.hettinger | 2008-03-24 09:17:39 +0100 (Mon, 24 Mar 2008) | 1 line Issue 2460: Make Ellipsis objects copyable. ........ r61842 | georg.brandl | 2008-03-24 10:34:34 +0100 (Mon, 24 Mar 2008) | 2 lines #1700821: add a note to audioop docs about signedness of sample formats. ........ r61851 | christian.heimes | 2008-03-24 20:57:42 +0100 (Mon, 24 Mar 2008) | 1 line Added quick hack for bzr ........ r61852 | christian.heimes | 2008-03-24 20:58:17 +0100 (Mon, 24 Mar 2008) | 1 line Added quick hack for bzr ........ r61853 | amaury.forgeotdarc | 2008-03-24 22:04:10 +0100 (Mon, 24 Mar 2008) | 4 lines Issue2469: Correct a typo I introduced at r61793: compilation error with UCS4 builds. All buildbots compile with UCS2... ........ r61863 | neal.norwitz | 2008-03-25 05:17:38 +0100 (Tue, 25 Mar 2008) | 2 lines Fix a bunch of UnboundLocalErrors when the tests fail. ........ r61864 | neal.norwitz | 2008-03-25 05:18:18 +0100 (Tue, 25 Mar 2008) | 2 lines Try to fix a bunch of compiler warnings on Win64. ........ r61869 | neal.norwitz | 2008-03-25 07:35:10 +0100 (Tue, 25 Mar 2008) | 3 lines Don't try to close a non-open file. Don't let file removal cause the test to fail. ........ r61870 | neal.norwitz | 2008-03-25 08:00:39 +0100 (Tue, 25 Mar 2008) | 7 lines Try to get this test to be more stable: * disable gc during the test run because we are spawning objects and there was an exception when calling Popen.__del__ * Always set an alarm handler so the process doesn't exit if the test fails (should probably add assertions on the value of hndl_called in more places) * Using a negative time causes Linux to treat it as zero, so disable that test. ........ r61874 | gregory.p.smith | 2008-03-25 08:31:28 +0100 (Tue, 25 Mar 2008) | 2 lines Use a 32-bit unsigned int here, a long is not needed. ........ r61889 | georg.brandl | 2008-03-25 12:59:51 +0100 (Tue, 25 Mar 2008) | 2 lines Move declarations to block start. ........
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d[type(Ellipsis)] = _deepcopy_atomic
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d[int] = _deepcopy_atomic
d[float] = _deepcopy_atomic
d[bool] = _deepcopy_atomic
try:
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d[complex] = _deepcopy_atomic
except NameError:
pass
d[bytes] = _deepcopy_atomic
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d[str] = _deepcopy_atomic
try:
d[types.CodeType] = _deepcopy_atomic
except AttributeError:
pass
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d[type] = _deepcopy_atomic
Merged revisions 55007-55179 via svnmerge from svn+ssh://pythondev@svn.python.org/python/branches/p3yk ........ r55077 | guido.van.rossum | 2007-05-02 11:54:37 -0700 (Wed, 02 May 2007) | 2 lines Use the new print syntax, at least. ........ r55142 | fred.drake | 2007-05-04 21:27:30 -0700 (Fri, 04 May 2007) | 1 line remove old cruftiness ........ r55143 | fred.drake | 2007-05-04 21:52:16 -0700 (Fri, 04 May 2007) | 1 line make this work with the new Python ........ r55162 | neal.norwitz | 2007-05-06 22:29:18 -0700 (Sun, 06 May 2007) | 1 line Get asdl code gen working with Python 2.3. Should continue to work with 3.0 ........ r55164 | neal.norwitz | 2007-05-07 00:00:38 -0700 (Mon, 07 May 2007) | 1 line Verify checkins to p3yk (sic) branch go to 3000 list. ........ r55166 | neal.norwitz | 2007-05-07 00:12:35 -0700 (Mon, 07 May 2007) | 1 line Fix this test so it runs again by importing warnings_test properly. ........ r55167 | neal.norwitz | 2007-05-07 01:03:22 -0700 (Mon, 07 May 2007) | 8 lines So long xrange. range() now supports values that are outside -sys.maxint to sys.maxint. floats raise a TypeError. This has been sitting for a long time. It probably has some problems and needs cleanup. Objects/rangeobject.c now uses 4-space indents since it is almost completely new. ........ r55171 | guido.van.rossum | 2007-05-07 10:21:26 -0700 (Mon, 07 May 2007) | 4 lines Fix two tests that were previously depending on significant spaces at the end of a line (and before that on Python 2.x print behavior that has no exact equivalent in 3.0). ........
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d[range] = _deepcopy_atomic
d[types.BuiltinFunctionType] = _deepcopy_atomic
d[types.FunctionType] = _deepcopy_atomic
d[weakref.ref] = _deepcopy_atomic
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def _deepcopy_list(x, memo):
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y = []
memo[id(x)] = y
for a in x:
y.append(deepcopy(a, memo))
return y
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d[list] = _deepcopy_list
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def _deepcopy_tuple(x, memo):
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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
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d[tuple] = _deepcopy_tuple
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def _deepcopy_dict(x, memo):
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y = {}
memo[id(x)] = y
for key, value in x.items():
y[deepcopy(key, memo)] = deepcopy(value, memo)
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return y
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d[dict] = _deepcopy_dict
if PyStringMap is not None:
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.
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 _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.items():
setattr(y, key, value)
return y
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del d
del types
# Helper for instance creation without calling __init__
class _EmptyClass:
pass
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def _test():
l = [None, 1, 2, 3.14, 'xyzzy', (1, 2), [3.14, 'abc'],
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{'abc': 'ABC'}, (), [], {}]
l1 = copy(l)
print(l1==l)
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l1 = map(copy, l)
print(l1==l)
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l1 = deepcopy(l)
print(l1==l)
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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.items():
setattr(self, key, value)
def __deepcopy__(self, memo=None):
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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)
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l2 = deepcopy(l)
print(l == l2)
print(l)
print(l2)
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l.append({l[1]: l, 'xyz': l[2]})
l3 = copy(l)
import reprlib
print(map(reprlib.repr, l))
print(map(reprlib.repr, l1))
print(map(reprlib.repr, l2))
print(map(reprlib.repr, l3))
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l3 = deepcopy(l)
print(map(reprlib.repr, l))
print(map(reprlib.repr, l1))
print(map(reprlib.repr, l2))
print(map(reprlib.repr, l3))
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if __name__ == '__main__':
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_test()