attr.converters Namespace Reference

Functions
	optional (converter)
	default_if_none (default=NOTHING, factory=None)
	to_bool (val)

Detailed Description

Commonly useful converters.

Function Documentation

default_if_none()

attr.converters.default_if_none	(		default = NOTHING,
			factory = None
	)

A converter that allows to replace `None` values by *default* or the result
of *factory*.

Args:
    default:
        Value to be used if `None` is passed. Passing an instance of
        `attrs.Factory` is supported, however the ``takes_self`` option is
        *not*.

    factory (typing.Callable):
        A callable that takes no parameters whose result is used if `None`
        is passed.

Raises:
    TypeError: If **neither** *default* or *factory* is passed.

    TypeError: If **both** *default* and *factory* are passed.

    ValueError:
        If an instance of `attrs.Factory` is passed with
        ``takes_self=True``.

.. versionadded:: 18.2.0

optional()

attr.converters.optional

(

converter

)

A converter that allows an attribute to be optional. An optional attribute
is one which can be set to `None`.

Type annotations will be inferred from the wrapped converter's, if it has
any.

Args:
    converter (typing.Callable):
        the converter that is used for non-`None` values.

.. versionadded:: 17.1.0

to_bool()

attr.converters.to_bool

(

val

)

Convert "boolean" strings (for example, from environment variables) to real
booleans.

Values mapping to `True`:

- ``True``
- ``"true"`` / ``"t"``
- ``"yes"`` / ``"y"``
- ``"on"``
- ``"1"``
- ``1``

Values mapping to `False`:

- ``False``
- ``"false"`` / ``"f"``
- ``"no"`` / ``"n"``
- ``"off"``
- ``"0"``
- ``0``

Raises:
    ValueError: For any other value.

.. versionadded:: 21.3.0