generic shallow and deep copying operations interface summary import copy x copy copyy make a shallow copy of y x copy deepcopyy 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 userdefined 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 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 shallow copy operation on arbitrary python objects see the module s doc string for more info treat it as a regular class deep copy operation on arbitrary python objects see the module s doc string for more info if is its own copy don t memoize we re not going to put the tuple in the memo but it s still important we check for it in case the tuple contains recursive mutable structures 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 aha this is the first one return a new object replacing specified fields with new values this is especially useful for immutable objects like named tuples or frozen dataclasses backward compatibility shallow copy operation on arbitrary python objects see the module s __doc__ string for more info treat it as a regular class deep copy operation on arbitrary python objects see the module s __doc__ string for more info if is its own copy don t memoize make sure x lives at least as long as d we re not going to put the tuple in the memo but it s still important we check for it in case the tuple contains recursive mutable structures copy instance methods 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 aha this is the first one return a new object replacing specified fields with new values this is especially useful for immutable objects like named tuples or frozen dataclasses
import types
import weakref
from copyreg import dispatch_table

class Error(Exception):
    pass
error = Error   

__all__ = ["Error", "copy", "deepcopy"]

def copy(x):
    

    cls = type(x)

    copier = _copy_dispatch.get(cls)
    if copier:
        return copier(x)

    if issubclass(cls, type):
        
        return _copy_immutable(x)

    copier = getattr(cls, "__copy__", None)
    if copier is not None:
        return copier(x)

    reductor = dispatch_table.get(cls)
    if reductor is not None:
        rv = reductor(x)
    else:
        reductor = getattr(x, "__reduce_ex__", None)
        if reductor is not None:
            rv = reductor(4)
        else:
            reductor = getattr(x, "__reduce__", None)
            if reductor:
                rv = reductor()
            else:
                raise Error("un(shallow)copyable object of type %s" % cls)

    if isinstance(rv, str):
        return x
    return _reconstruct(x, None, *rv)


_copy_dispatch = d = {}

def _copy_immutable(x):
    return x
for t in (types.NoneType, int, float, bool, complex, str, tuple,
          bytes, frozenset, type, range, slice, property,
          types.BuiltinFunctionType, types.EllipsisType,
          types.NotImplementedType, types.FunctionType, types.CodeType,
          weakref.ref):
    d[t] = _copy_immutable

d[list] = list.copy
d[dict] = dict.copy
d[set] = set.copy
d[bytearray] = bytearray.copy

del d, t

def deepcopy(x, memo=None, _nil=[]):
    

    d = id(x)
    if memo is None:
        memo = {}
    else:
        y = memo.get(d, _nil)
        if y is not _nil:
            return y

    cls = type(x)

    copier = _deepcopy_dispatch.get(cls)
    if copier is not None:
        y = copier(x, memo)
    else:
        if issubclass(cls, type):
            y = _deepcopy_atomic(x, memo)
        else:
            copier = getattr(x, "__deepcopy__", None)
            if copier is not None:
                y = copier(memo)
            else:
                reductor = dispatch_table.get(cls)
                if reductor:
                    rv = reductor(x)
                else:
                    reductor = getattr(x, "__reduce_ex__", None)
                    if reductor is not None:
                        rv = reductor(4)
                    else:
                        reductor = getattr(x, "__reduce__", None)
                        if reductor:
                            rv = reductor()
                        else:
                            raise Error(
                                "un(deep)copyable object of type %s" % cls)
                if isinstance(rv, str):
                    y = x
                else:
                    y = _reconstruct(x, memo, *rv)

    
    if y is not x:
        memo[d] = y
        _keep_alive(x, memo) 
    return y

_deepcopy_dispatch = d = {}

def _deepcopy_atomic(x, memo):
    return x
d[types.NoneType] = _deepcopy_atomic
d[types.EllipsisType] = _deepcopy_atomic
d[types.NotImplementedType] = _deepcopy_atomic
d[int] = _deepcopy_atomic
d[float] = _deepcopy_atomic
d[bool] = _deepcopy_atomic
d[complex] = _deepcopy_atomic
d[bytes] = _deepcopy_atomic
d[str] = _deepcopy_atomic
d[types.CodeType] = _deepcopy_atomic
d[type] = _deepcopy_atomic
d[range] = _deepcopy_atomic
d[types.BuiltinFunctionType] = _deepcopy_atomic
d[types.FunctionType] = _deepcopy_atomic
d[weakref.ref] = _deepcopy_atomic
d[property] = _deepcopy_atomic

def _deepcopy_list(x, memo, deepcopy=deepcopy):
    y = []
    memo[id(x)] = y
    append = y.append
    for a in x:
        append(deepcopy(a, memo))
    return y
d[list] = _deepcopy_list

def _deepcopy_tuple(x, memo, deepcopy=deepcopy):
    y = [deepcopy(a, memo) for a in x]
    
    
    try:
        return memo[id(x)]
    except KeyError:
        pass
    for k, j in zip(x, y):
        if k is not j:
            y = tuple(y)
            break
    else:
        y = x
    return y
d[tuple] = _deepcopy_tuple

def _deepcopy_dict(x, memo, deepcopy=deepcopy):
    y = {}
    memo[id(x)] = y
    for key, value in x.items():
        y[deepcopy(key, memo)] = deepcopy(value, memo)
    return y
d[dict] = _deepcopy_dict

def _deepcopy_method(x, memo): 
    return type(x)(x.__func__, deepcopy(x.__self__, memo))
d[types.MethodType] = _deepcopy_method

del d

def _keep_alive(x, memo):
    
    try:
        memo[id(memo)].append(x)
    except KeyError:
        
        memo[id(memo)]=[x]

def _reconstruct(x, memo, func, args,
                 state=None, listiter=None, dictiter=None,
                 *, deepcopy=deepcopy):
    deep = memo is not None
    if deep and args:
        args = (deepcopy(arg, memo) for arg in args)
    y = func(*args)
    if deep:
        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.items():
                    setattr(y, key, value)

    if listiter is not None:
        if deep:
            for item in listiter:
                item = deepcopy(item, memo)
                y.append(item)
        else:
            for item in listiter:
                y.append(item)
    if dictiter is not None:
        if deep:
            for key, value in dictiter:
                key = deepcopy(key, memo)
                value = deepcopy(value, memo)
                y[key] = value
        else:
            for key, value in dictiter:
                y[key] = value
    return y

del types, weakref


def replace(obj, /, **changes):
    
    cls = obj.__class__
    func = getattr(cls, '__replace__', None)
    if func is None:
        raise TypeError(f"replace() does not support {cls.__name__} objects")
    return func(obj, **changes)