"""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.
"""
# XXX need to support copy_reg here too...
import types
error = 'copy.error'
Error = error # backward compatibility
def copy(x):
"""Shallow copy operation on arbitrary Python objects.
See the module's __doc__ string for more info.
"""
try:
copierfunction = _copy_dispatch[type(x)]
except KeyError:
try:
copier = x.__copy__
except AttributeError:
raise error, \
"un(shallow)copyable object of type %s" % type(x)
y = copier()
else:
y = copierfunction(x)
return y
_copy_dispatch = d = {}
def _copy_atomic(x):
return x
d[types.NoneType] = _copy_atomic
d[types.IntType] = _copy_atomic
d[types.LongType] = _copy_atomic
if hasattr(types, FloatType):
d[types.FloatType] = _copy_atomic
d[types.StringType] = _copy_atomic
if hasattr(types, CodeType):
d[types.CodeType] = _copy_atomic
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
def _copy_inst(x):
if hasattr(x, '__copy__'):
return x.__copy__()
if hasattr(x, '__getinitargs__'):
args = x.__getinitargs__()
y = apply(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):
"""Deep copy operation on arbitrary Python objects.
See the module's __doc__ string for more info.
"""
if memo is None:
memo = {}
d = id(x)
if memo.has_key(d):
return memo[d]
try:
copierfunction = _deepcopy_dispatch[type(x)]
except KeyError:
try:
copier = x.__deepcopy__
except AttributeError:
raise error, \
"un-deep-copyable object of type %s" % type(x)
y = copier(memo)
else:
y = copierfunction(x, memo)
memo[d] = y
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
if hasattr(types, FloatType):
d[types.FloatType] = _deepcopy_atomic
d[types.StringType] = _deepcopy_atomic
d[types.CodeType] = _deepcopy_atomic
d[types.TypeType] = _deepcopy_atomic
d[types.XRangeType] = _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 in x.keys():
y[deepcopy(key, memo)] = deepcopy(x[key], memo)
return y
d[types.DictionaryType] = _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__()
_keep_alive(args, memo)
args = deepcopy(args, memo)
y = apply(x.__class__, args)
else:
y = _EmptyClass()
y.__class__ = x.__class__
memo[id(x)] = y
if hasattr(x, '__getstate__'):
state = x.__getstate__()
_keep_alive(state, memo)
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
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 in state.keys():
setattr(self, key, state[key])
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()
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