Function field

Lib/dataclasses.py:391–412

Return an object to identify dataclass fields. default is the default value of the field. default_factory is a 0-argument function called to initialize a field's value. If init is true, the field will be a parameter to the class's __init__() function. If repr is true, the field w

(*, default=MISSING, default_factory=MISSING, init=True, repr=True,
          hash=None, compare=True, metadata=None, kw_only=MISSING, doc=None)

# so that a type checker can be told (via overloads) that this is a
# function whose type depends on its parameters.
def field(*, default=MISSING, default_factory=MISSING, init=True, repr=True,
          hash=None, compare=True, metadata=None, kw_only=MISSING, doc=None):
    """Return an object to identify dataclass fields.

    default is the default value of the field.  default_factory is a
    0-argument function called to initialize a field's value.  If init
    is true, the field will be a parameter to the class's __init__()
    function.  If repr is true, the field will be included in the
    object's repr().  If hash is true, the field will be included in the
    object's hash().  If compare is true, the field will be used in
    comparison functions.  metadata, if specified, must be a mapping
    which is stored but not otherwise examined by dataclass.  If kw_only
    is true, the field will become a keyword-only parameter to
    __init__().  doc is an optional docstring for this field.

    It is an error to specify both default and default_factory.
    """

    if default is not MISSING and default_factory is not MISSING:
        raise ValueError('cannot specify both default and default_factory')
    return Field(default, default_factory, init, repr, hash, compare,
                 metadata, kw_only, doc)


def _fields_in_init_order(fields):