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DefaultDict

Bases: FlatDict

DefaultDict inherits from FlatDict and incorporates support of default_factory in the same manner as collections.defaultdict. If default_factory is not None, the value will be set to default_factory() when you access a key that does not exist in DefaultDict.

You may specify DefaultDict(default_factory=FlatDict) when creating DefaultDict or by calling dict.setattr('default_factory', FlatDict) for existing DefaultDict objects.

Note that just like collections.defaultdict, default_factory() is called without any arguments.

Attributes:

Name Type Description
default_factory Optional[Callable]

Default factory for defaultdict behaviour.

Raises:

Type Description
TypeError

If default_factory is not callable.
Notes

Unlike collections.defaultdict, DefaultDict will not automatically create entries when name starts and ends with __. This is to avoid conflicts with Python magic methods. You can still creates them manually with DefaultDict.fromkeys or DefaultDict.add.

Examples:

Python Console Session
>>> d = DefaultDict(list)
>>> d.a.append(1)
>>> d.a
[1]
>>> d = DefaultDict([])
Traceback (most recent call last):
TypeError: `default_factory=[]` must be Callable, but got <class 'list'>.
Source code in chanfig/default_dict.py
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class DefaultDict(FlatDict):
    r"""
    `DefaultDict` inherits from `FlatDict` and incorporates support of `default_factory`
    in the same manner as `collections.defaultdict`.
    If `default_factory is not None`, the value will be set to `default_factory()`
    when you access a key that does not exist in `DefaultDict`.

    You may specify `DefaultDict(default_factory=FlatDict)` when creating `DefaultDict` or
    by calling `dict.setattr('default_factory', FlatDict)` for existing `DefaultDict` objects.

    Note that just like `collections.defaultdict`, `default_factory()` is called without any arguments.

    Attributes:
        default_factory: Default factory for defaultdict behaviour.

    Raises:
        TypeError: If `default_factory` is not callable.

    Notes:
        Unlike `collections.defaultdict`, `DefaultDict` will not automatically create entries when name starts and ends
        with `__`. This is to avoid conflicts with Python magic methods.
        You can still creates them manually with `DefaultDict.fromkeys` or `DefaultDict.add`.

    Examples:
        >>> d = DefaultDict(list)
        >>> d.a.append(1)
        >>> d.a
        [1]
        >>> d = DefaultDict([])
        Traceback (most recent call last):
        TypeError: `default_factory=[]` must be Callable, but got <class 'list'>.
    """

    default_factory: Optional[Callable] = None

    def __init__(  # pylint: disable=W1113
        self, default_factory: Callable | None = None, *args: Any, **kwargs: Any
    ) -> None:
        super().__init__(*args, **kwargs)
        if default_factory is not None:
            if callable(default_factory):
                self.setattr("default_factory", default_factory)
            else:
                raise TypeError(
                    f"`default_factory={default_factory}` must be Callable, but got {type(default_factory)}."
                )

    def __missing__(self, name: Any, default=Null) -> Any:  # pylint: disable=R1710
        if default is Null:
            if self.getattr("default_factory", None) in (None, Null) or (name.startswith("__") and name.endswith("__")):
                raise KeyError(name) from None
            default = self.getattr("default_factory")()
        if isinstance(default, FlatDict):
            default.__dict__.update(self.__dict__)
        super().set(name, default)
        return default

    def __repr__(self) -> str:
        if self.default_factory is None:
            return super().__repr__()
        super_repr = super().__repr__()[len(self.__class__.__name__) :]  # noqa: E203
        if len(super_repr) == 2:
            return f"{self.__class__.__name__}({self.default_factory}, )"
        return f"{self.__class__.__name__}({self.default_factory}," + super_repr[1:]

    def add(self, name: Any):
        r"""
        Add a new default factory to the dictionary.

        Args:
            name:

        Raises:
            ValueError: If `default_factory` is None.

        Examples:
            >>> d = DefaultDict(default_factory=DefaultDict)
            >>> d.add('d')
            DefaultDict()
            >>> d.get('d')
            DefaultDict()
            >>> d['n'] = 'chang'
            >>> d.n
            'chang'
            >>> d.n = 'liu'
            >>> d['n']
            'liu'
            >>> d = DefaultDict()
            >>> d.add('a')
            Traceback (most recent call last):
            ValueError: Cannot add to a DefaultDict with no default_factory
        """
        if self.default_factory is None:
            raise ValueError("Cannot add to a DefaultDict with no default_factory")
        self.set(name, self.default_factory())  # pylint: disable=E1102
        return self.get(name)

add(name)

Add a new default factory to the dictionary.

Parameters:

Name Type Description Default
name Any
required

Raises:

Type Description
ValueError

If default_factory is None.

Examples:

Python Console Session
>>> d = DefaultDict(default_factory=DefaultDict)
>>> d.add('d')
DefaultDict()
>>> d.get('d')
DefaultDict()
>>> d['n'] = 'chang'
>>> d.n
'chang'
>>> d.n = 'liu'
>>> d['n']
'liu'
>>> d = DefaultDict()
>>> d.add('a')
Traceback (most recent call last):
ValueError: Cannot add to a DefaultDict with no default_factory
Source code in chanfig/default_dict.py
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def add(self, name: Any):
    r"""
    Add a new default factory to the dictionary.

    Args:
        name:

    Raises:
        ValueError: If `default_factory` is None.

    Examples:
        >>> d = DefaultDict(default_factory=DefaultDict)
        >>> d.add('d')
        DefaultDict()
        >>> d.get('d')
        DefaultDict()
        >>> d['n'] = 'chang'
        >>> d.n
        'chang'
        >>> d.n = 'liu'
        >>> d['n']
        'liu'
        >>> d = DefaultDict()
        >>> d.add('a')
        Traceback (most recent call last):
        ValueError: Cannot add to a DefaultDict with no default_factory
    """
    if self.default_factory is None:
        raise ValueError("Cannot add to a DefaultDict with no default_factory")
    self.set(name, self.default_factory())  # pylint: disable=E1102
    return self.get(name)