source: trunk/essentials/dev-lang/python/Lib/copy.py@ 3393

"""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
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,
          types.FunctionType):
    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: