Class SysModulesSnapshot

src/_pytest/pytester.py:627–638

class SysModulesSnapshot:
    def __init__(self, preserve: Callable[[str], bool] | None = None) -> None:
        self.__preserve = preserve
        self.__saved = dict(sys.modules)

    def restore(self) -> None:
        if self.__preserve:
            self.__saved.update(
                (k, m) for k, m in sys.modules.items() if self.__preserve(k)
            )
        sys.modules.clear()
        sys.modules.update(self.__saved)


class SysPathsSnapshot: