Utilities¶

Bases: type

Metaclass for Singleton Classes.

Source code in chanfig/utils.py

Python
class Singleton(type):
    r"""
    Metaclass for Singleton Classes.
    """

    __instances__: Mapping[type, object] = {}

    def __call__(cls, *args: Any, **kwargs: Any):
        if cls not in cls.__instances__:
            cls.__instances__[cls] = super().__call__(*args, **kwargs)  # type: ignore[index]
        return cls.__instances__[cls]

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chanfig.utils.Null¶

Null is an instance of NULL.

Since the metaclass of NULL is Singleton, it is advised to use obj is Null to determine if obj is Null.

NULL class.

get method in CHANfiG may accept None or Ellipse(...) as value of default. Therefore, it is mandatory to have a different default value for default.

Null is an instance of NULL and is recommended to be used as obj is Null.

Source code in chanfig/utils.py

Python
class NULL(metaclass=Singleton):
    r"""
    NULL class.

    `get` method in CHANfiG may accept `None` or `Ellipse`(`...`) as value of `default`.
    Therefore, it is mandatory to have a different default value for `default`.

    `Null` is an instance of `NULL` and is recommended to be used as `obj is Null`.
    """

    def __repr__(self):
        return "Null"

    def __nonzero__(self):
        return False

    def __len__(self):
        return 0

    def __call__(self, *args: Any, **kwargs: Any):
        return self

    def __contains__(self, name):
        return False

    def __iter__(self):
        return self

    def __next__(self):
        raise StopIteration

    def __getattr__(self, name):
        return self

    def __getitem__(self, index):
        return self

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Bases: JSONEncoder

JSON encoder for Config.

Source code in chanfig/utils.py

Python
class JsonEncoder(JSONEncoder):
    r"""
    JSON encoder for Config.
    """

    def default(self, o: Any) -> Any:
        if hasattr(o, "__json__"):
            return o.__json__()
        return super().default(o)

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Bases: SafeDumper

YAML Dumper for Config.

Source code in chanfig/utils.py

Python
class YamlDumper(SafeDumper):  # pylint: disable=R0903
    r"""
    YAML Dumper for Config.
    """

    def increase_indent(self, flow: bool = False, indentless: bool = False):  # pylint: disable=W0235
        return super().increase_indent(flow, indentless)

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Bases: SafeLoader

YAML Loader for Config.

Source code in chanfig/utils.py

Python
class YamlLoader(SafeLoader):  # pylint: disable=R0901,R0903
    r"""
    YAML Loader for Config.
    """

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