_KEYWORD_ONLY = _ParameterKind.KEYWORD_ONLY

_VAR_KEYWORD = _ParameterKind.VAR_KEYWORD

_PARAM_NAME_MAPPING = {

_POSITIONAL_ONLY: 'positional-only',

_POSITIONAL_OR_KEYWORD: 'positional or keyword',

_VAR_POSITIONAL: 'variadic positional',

_KEYWORD_ONLY: 'keyword-only',

_VAR_KEYWORD: 'variadic keyword'

}

_get_paramkind_descr = _PARAM_NAME_MAPPING.__getitem__

class Parameter:

"""Represents a parameter in a function signature.

empty = _empty

def __init__(self, name, kind, *, default=_empty, annotation=_empty):

if kind not in (_POSITIONAL_ONLY, _POSITIONAL_OR_KEYWORD,

_VAR_POSITIONAL, _KEYWORD_ONLY, _VAR_KEYWORD):

raise ValueError("invalid value for 'Parameter.kind' attribute")

self._kind = kind

try:

self._kind = _ParameterKind(kind)

except ValueError:

raise ValueError(f'value {kind!r} is not a valid Parameter.kind')

if default is not _empty:

if kind in (_VAR_POSITIONAL, _VAR_KEYWORD):

msg = '{} parameters cannot have default values'.format(kind)

if self._kind in (_VAR_POSITIONAL, _VAR_KEYWORD):

msg = '{} parameters cannot have default values'

msg = msg.format(_get_paramkind_descr(self._kind))

raise ValueError(msg)

self._default = default

self._annotation = annotation

raise ValueError('name is a required attribute for Parameter')

if not isinstance(name, str):

raise TypeError("name must be a str, not a {!r}".format(name))

msg = 'name must be a str, not a {}'.format(type(name).__name__)

raise TypeError(msg)

if name[0] == '.' and name[1:].isdigit():

# These are implicit arguments generated by comprehensions. In

# order to provide a friendlier interface to users, we recast

# their name as "implicitN" and treat them as positional-only.

# See issue 19611.

if kind != _POSITIONAL_OR_KEYWORD:

raise ValueError(

'implicit arguments must be passed in as {}'.format(

_POSITIONAL_OR_KEYWORD

)

if self._kind != _POSITIONAL_OR_KEYWORD:

msg = (

'implicit arguments must be passed as '

'positional or keyword arguments, not {}'

)

msg = msg.format(_get_paramkind_descr(self._kind))

raise ValueError(msg)

self._kind = _POSITIONAL_ONLY

name = 'implicit{}'.format(name[1:])

name = param.name

if kind < top_kind:

msg = 'wrong parameter order: {!r} before {!r}'

msg = msg.format(top_kind, kind)

msg = (

'wrong parameter order: {} parameter before {} '

'parameter'

)

msg = msg.format(_get_paramkind_descr(top_kind),

_get_paramkind_descr(kind))

raise ValueError(msg)

elif kind > top_kind:

kind_defaults = False