Mini Shell

import os
import sys
import types
from collections.abc import MutableSequence
from functools import total_ordering
from typing import Type

__version__ = "1.4.0"

__all__ = ("FrozenList", "PyFrozenList")  # type: Tuple[str, ...]


NO_EXTENSIONS = bool(os.environ.get("FROZENLIST_NO_EXTENSIONS"))  # type: bool


@total_ordering
class FrozenList(MutableSequence):
    __slots__ = ("_frozen", "_items")

    if sys.version_info >= (3, 9):
        __class_getitem__ = classmethod(types.GenericAlias)
    else:

        @classmethod
        def __class_getitem__(cls: Type["FrozenList"]) -> Type["FrozenList"]:
            return cls

    def __init__(self, items=None):
        self._frozen = False
        if items is not None:
            items = list(items)
        else:
            items = []
        self._items = items

    @property
    def frozen(self):
        return self._frozen

    def freeze(self):
        self._frozen = True

    def __getitem__(self, index):
        return self._items[index]

    def __setitem__(self, index, value):
        if self._frozen:
            raise RuntimeError("Cannot modify frozen list.")
        self._items[index] = value

    def __delitem__(self, index):
        if self._frozen:
            raise RuntimeError("Cannot modify frozen list.")
        del self._items[index]

    def __len__(self):
        return self._items.__len__()

    def __iter__(self):
        return self._items.__iter__()

    def __reversed__(self):
        return self._items.__reversed__()

    def __eq__(self, other):
        return list(self) == other

    def __le__(self, other):
        return list(self) <= other

    def insert(self, pos, item):
        if self._frozen:
            raise RuntimeError("Cannot modify frozen list.")
        self._items.insert(pos, item)

    def __repr__(self):
        return f"<FrozenList(frozen={self._frozen}, {self._items!r})>"

    def __hash__(self):
        if self._frozen:
            return hash(tuple(self))
        else:
            raise RuntimeError("Cannot hash unfrozen list.")


PyFrozenList = FrozenList


try:
    from ._frozenlist import FrozenList as CFrozenList  # type: ignore

    if not NO_EXTENSIONS:  # pragma: no cover
        FrozenList = CFrozenList  # type: ignore
except ImportError:  # pragma: no cover
    pass