Class BaseSettings

scrapy/settings/__init__.py:83–702

Instances of this class behave like dictionaries, but store priorities along with their ``(key, value)`` pairs, and can be frozen (i.e. marked immutable). Key-value entries can be passed on initialization with the ``values`` argument, and they would take the ``priority`` level

class BaseSettings(MutableMapping[_SettingsKey, Any]):
    """
    Instances of this class behave like dictionaries, but store priorities
    along with their ``(key, value)`` pairs, and can be frozen (i.e. marked
    immutable).

    Key-value entries can be passed on initialization with the ``values``
    argument, and they would take the ``priority`` level (unless ``values`` is
    already an instance of :class:`~scrapy.settings.BaseSettings`, in which
    case the existing priority levels will be kept).  If the ``priority``
    argument is a string, the priority name will be looked up in
    :attr:`~scrapy.settings.SETTINGS_PRIORITIES`. Otherwise, a specific integer
    should be provided.

    Once the object is created, new settings can be loaded or updated with the
    :meth:`~scrapy.settings.BaseSettings.set` method, and can be accessed with
    the square bracket notation of dictionaries, or with the
    :meth:`~scrapy.settings.BaseSettings.get` method of the instance and its
    value conversion variants. When requesting a stored key, the value with the
    highest priority will be retrieved.
    """

    __default = object()

    def __init__(self, values: _SettingsInput = None, priority: int | str = "project"):
        self.frozen: bool = False
        self.attributes: dict[_SettingsKey, SettingsAttribute] = {}
        if values:
            self.update(values, priority)

    def __getitem__(self, opt_name: _SettingsKey) -> Any:
        if opt_name not in self:
            return None
        return self.attributes[opt_name].value

    def __contains__(self, name: Any) -> bool:
        return name in self.attributes

    def add_to_list(self, name: _SettingsKey, item: Any) -> None:
        """Append *item* to the :class:`list` setting with the specified *name*
        if *item* is not already in that list.

        This change is applied regardless of the priority of the *name*
        setting. The setting priority is not affected by this change either.
        """
        value: list[str] = self.getlist(name)
        if item not in value:
            self.set(name, [*value, item], self.getpriority(name) or 0)

    def remove_from_list(self, name: _SettingsKey, item: Any) -> None:
        """Remove *item* from the :class:`list` setting with the specified
        *name*.

        If *item* is missing, raise :exc:`ValueError`.

        This change is applied regardless of the priority of the *name*
        setting. The setting priority is not affected by this change either.
        """