enum.py

import sys
import builtins as bltns
from functools import partial
from types import MappingProxyType, DynamicClassAttribute


__all__ = [
        'EnumType', 'EnumMeta', 'EnumDict',
        'Enum', 'IntEnum', 'StrEnum', 'Flag', 'IntFlag', 'ReprEnum',
        'auto', 'unique', 'property', 'verify', 'member', 'nonmember',
        'FlagBoundary', 'STRICT', 'CONFORM', 'EJECT', 'KEEP',
        'global_flag_repr', 'global_enum_repr', 'global_str', 'global_enum',
        'EnumCheck', 'CONTINUOUS', 'NAMED_FLAGS', 'UNIQUE',
        'pickle_by_global_name', 'pickle_by_enum_name',
        ]


# Dummy value for Enum and Flag as there are explicit checks for them
# before they have been created.
# This is also why there are checks in EnumType like `if Enum is not None`
Enum = Flag = EJECT = _stdlib_enums = ReprEnum = None

class nonmember(object):
    """
    Protects item from becoming an Enum member during class creation.
    """
    def __init__(self, value):
        self.value = value

class member(object):
    """
    Forces item to become an Enum member during class creation.
    """
    def __init__(self, value):
        self.value = value

def _is_descriptor(obj):
    """
    Returns True if obj is a descriptor, False otherwise.
    """
    return not isinstance(obj, partial) and (
            hasattr(obj, '__get__') or
            hasattr(obj, '__set__') or
            hasattr(obj, '__delete__')
            )

def _is_dunder(name):
    """
    Returns True if a __dunder__ name, False otherwise.
    """
    return (
            len(name) > 4 and
            name[:2] == name[-2:] == '__' and
            name[2] != '_' and
            name[-3] != '_'
            )

def _is_sunder(name):
    """
    Returns True if a _sunder_ name, False otherwise.
    """
    return (
            len(name) > 2 and
            name[0] == name[-1] == '_' and
            name[1] != '_' and
            name[-2] != '_'
            )

def _is_internal_class(cls_name, obj):
    # do not use `re` as `re` imports `enum`
    if not isinstance(obj, type):
        return False
    qualname = getattr(obj, '__qualname__', '')
    s_pattern = cls_name + '.' + getattr(obj, '__name__', '')
    e_pattern = '.' + s_pattern
    return qualname == s_pattern or qualname.endswith(e_pattern)

def _is_private(cls_name, name):
    # do not use `re` as `re` imports `enum`
    pattern = '_%s__' % (cls_name, )
    pat_len = len(pattern)
    if (
            len(name) > pat_len
            and name.startswith(pattern)
            and (name[-1] != '_' or name[-2] != '_')
        ):
        return True
    else:
        return False

def _is_single_bit(num):
    """
    True if only one bit set in num (should be an int)
    """
    if num == 0:
        return False
    num &= num - 1
    return num == 0

def _make_class_unpicklable(obj):
    """
    Make the given obj un-picklable.

    obj should be either a dictionary, or an Enum
    """
    def _break_on_call_reduce(self, proto):
        raise TypeError('%r cannot be pickled' % self)
    if isinstance(obj, dict):
        obj['__reduce_ex__'] = _break_on_call_reduce
        obj['__module__'] = '<unknown>'
    else:
        setattr(obj, '__reduce_ex__', _break_on_call_reduce)
        setattr(obj, '__module__', '<unknown>')

def _iter_bits_lsb(num):
    # num must be a positive integer
    original = num
    if isinstance(num, Enum):
        num = num.value
    if num < 0:
        raise ValueError('%r is not a positive integer' % original)
    while num:
        b = num & (~num + 1)
        yield b
        num ^= b

def show_flag_values(value):
    return list(_iter_bits_lsb(value))

def bin(num, max_bits=None):
    """
    Like built-in bin(), except negative values are represented in
    twos-compliment, and the leading bit always indicates sign
    (0=positive, 1=negative).

    >>> bin(10)
    '0b0 1010'
    >>> bin(~10)   # ~10 is -11
    '0b1 0101'
    """

    ceiling = 2 ** (num).bit_length()
    if num >= 0:
        s = bltns.bin(num + ceiling).replace('1', '0', 1)
    else:
        s = bltns.bin(~num ^ (ceiling - 1) + ceiling)
    sign = s[:3]
    digits = s[3:]
    if max_bits is not None:
        if len(digits) < max_bits:
            digits = (sign[-1] * max_bits + digits)[-max_bits:]
    return "%s %s" % (sign, digits)

def _dedent(text):
    """
    Like textwrap.dedent.  Rewritten because we cannot import textwrap.
    """
    lines = text.split('\n')
    for i, ch in enumerate(lines[0]):
        if ch != ' ':
            break
    for j, l in enumerate(lines):
        lines[j] = l[i:]
    return '\n'.join(lines)

class _not_given:
    def __repr__(self):
        return('<not given>')
_not_given = _not_given()

class _auto_null:
    def __repr__(self):
        return '_auto_null'
_auto_null = _auto_null()

class auto:
    """
    Instances are replaced with an appropriate value in Enum class suites.
    """
    def __init__(self, value=_auto_null):
        self.value = value

    def __repr__(self):
        return "auto(%r)" % self.value

class property(DynamicClassAttribute):
    """
    This is a descriptor, used to define attributes that act differently
    when accessed through an enum member and through an enum class.
    Instance access is the same as property(), but access to an attribute
    through the enum class will instead look in the class' _member_map_ for
    a corresponding enum member.
    """

    member = None
    _attr_type = None
    _cls_type = None

    def __get__(self, instance, ownerclass=None):
        if instance is None:
            if self.member is not None:
                return self.member
            else:
                raise AttributeError(
                        '%r has no attribute %r' % (ownerclass, self.name)
                        )
        if self.fget is not None:
            # use previous enum.property
            return self.fget(instance)
        elif self._attr_type == 'attr':
            # look up previous attibute
            return getattr(self._cls_type, self.name)
        elif self._attr_type == 'desc':
            # use previous descriptor
            return getattr(instance._value_, self.name)
        # look for a member by this name.
        try:
            return ownerclass._member_map_[self.name]
        except KeyError:
            raise AttributeError(
                    '%r has no attribute %r' % (ownerclass, self.name)
                    ) from None

    def __set__(self, instance, value):
        if self.fset is not None:
            return self.fset(instance, value)
        raise AttributeError(
                "<enum %r> cannot set attribute %r" % (self.clsname, self.name)
                )

    def __delete__(self, instance):
        if self.fdel is not None:
            return self.fdel(instance)
        raise AttributeError(
                "<enum %r> cannot delete attribute %r" % (self.clsname, self.name)
                )

    def __set_name__(self, ownerclass, name):
        self.name = name
        self.clsname = ownerclass.__name__


class _proto_member:
    """
    intermediate step for enum members between class execution and final creation
    """

    def __init__(self, value):
        self.value = value

    def __set_name__(self, enum_class, member_name):
        """
        convert each quasi-member into an instance of the new enum class
        """
        # first step: remove ourself from enum_class
        delattr(enum_class, member_name)
        # second step: create member based on enum_class
        value = self.value
        if not isinstance(value, tuple):
            args = (value, )
        else:
            args = value
        if enum_class._member_type_ is tuple:   # special case for tuple enums
            args = (args, )     # wrap it one more time
        if not enum_class._use_args_:
            enum_member = enum_class._new_member_(enum_class)
        else:
            enum_member = enum_class._new_member_(enum_class, *args)
        if not hasattr(enum_member, '_value_'):
            if enum_class._member_type_ is object:
                enum_member._value_ = value
            else:
                try:
                    enum_member._value_ = enum_class._member_type_(*args)
                except Exception as exc:
                    new_exc = TypeError(
                            '_value_ not set in __new__, unable to create it'
                            )
                    new_exc.__cause__ = exc
                    raise new_exc
        value = enum_member._value_
        enum_member._name_ = member_name
        enum_member.__objclass__ = enum_class
        enum_member.__init__(*args)
        enum_member._sort_order_ = len(enum_class._member_names_)

        if Flag is not None and issubclass(enum_class, Flag):
            if isinstance(value, int):
                enum_class._flag_mask_ |= value
                if _is_single_bit(value):
                    enum_class._singles_mask_ |= value
            enum_class._all_bits_ = 2 ** ((enum_class._flag_mask_).bit_length()) - 1

        # If another member with the same value was already defined, the
        # new member becomes an alias to the existing one.
        try:
            try:
                # try to do a fast lookup to avoid the quadratic loop
                enum_member = enum_class._value2member_map_[value]
            except TypeError:
                for name, canonical_member in enum_class._member_map_.items():
                    if canonical_member._value_ == value:
                        enum_member = canonical_member
                        break
                else:
                    raise KeyError
        except KeyError:
            # this could still be an alias if the value is multi-bit and the
            # class is a flag class
            if (
                    Flag is None
                    or not issubclass(enum_class, Flag)
                ):
                # no other instances found, record this member in _member_names_
                enum_class._member_names_.append(member_name)
            elif (
                    Flag is not None
                    and issubclass(enum_class, Flag)
                    and isinstance(value, int)
                    and _is_single_bit(value)
                ):
                # no other instances found, record this member in _member_names_
                enum_class._member_names_.append(member_name)

        enum_class._add_member_(member_name, enum_member)
        try:
            # This may fail if value is not hashable. We can't add the value
            # to the map, and by-value lookups for this value will be
            # linear.
            enum_class._value2member_map_.setdefault(value, enum_member)
            if value not in enum_class._hashable_values_:
                enum_class._hashable_values_.append(value)
        except TypeError:
            # keep track of the value in a list so containment checks are quick
            enum_class._unhashable_values_.append(value)
            enum_class._unhashable_values_map_.setdefault(member_name, []).append(value)


class EnumDict(dict):
    """
    Track enum member order and ensure member names are not reused.

    EnumType will use the names found in self._member_names as the
    enumeration member names.
    """
    def __init__(self, cls_name=None):
        super().__init__()
        self._member_names = {} # use a dict -- faster look-up than a list, and keeps insertion order since 3.7
        self._last_values = []
        self._ignore = []
        self._auto_called = False
        self._cls_name = cls_name

    def __setitem__(self, key, value):
        """
        Changes anything not dundered or not a descriptor.

        If an enum member name is used twice, an error is raised; duplicate
        values are not checked for.

        Single underscore (sunder) names are reserved.
        """
        if self._cls_name is not None and _is_private(self._cls_name, key):
            # do nothing, name will be a normal attribute
            pass
        elif _is_sunder(key):
            if key not in (
                    '_order_',
                    '_generate_next_value_', '_numeric_repr_', '_missing_', '_ignore_',
                    '_iter_member_', '_iter_member_by_value_', '_iter_member_by_def_',
                    '_add_alias_', '_add_value_alias_',
                    # While not in use internally, those are common for pretty
                    # printing and thus excluded from Enum's reservation of
                    # _sunder_ names
                    ) and not key.startswith('_repr_'):
                raise ValueError(
                        '_sunder_ names, such as %r, are reserved for future Enum use'
                        % (key, )
                        )
            if key == '_generate_next_value_':
                # check if members already defined as auto()
                if self._auto_called:
                    raise TypeError("_generate_next_value_ must be defined before members")
                _gnv = value.__func__ if isinstance(value, staticmethod) else value
                setattr(self, '_generate_next_value', _gnv)
            elif key == '_ignore_':
                if isinstance(value, str):
                    value = value.replace(',',' ').split()
                else:
                    value = list(value)
                self._ignore = value
                already = set(value) & set(self._member_names)
                if already:
                    raise ValueError(
                            '_ignore_ cannot specify already set names: %r'
                            % (already, )
                            )
        elif _is_dunder(key):
            if key == '__order__':
                key = '_order_'
        elif key in self._member_names:
            # descriptor overwriting an enum?
            raise TypeError('%r already defined as %r' % (key, self[key]))
        elif key in self._ignore:
            pass
        elif isinstance(value, nonmember):
            # unwrap value here; it won't be processed by the below `else`
            value = value.value
        elif isinstance(value, partial):
            import warnings
            warnings.warn('functools.partial will be a method descriptor '
                          'in future Python versions; wrap it in '
                          'enum.member() if you want to preserve the '
                          'old behavior', FutureWarning, stacklevel=2)
        elif _is_descriptor(value):
            pass
        elif self._cls_name is not None and _is_internal_class(self._cls_name, value):
            # do nothing, name will be a normal attribute
            pass
        else:
            if key in self:
                # enum overwriting a descriptor?
                raise TypeError('%r already defined as %r' % (key, self[key]))
            elif isinstance(value, member):
                # unwrap value here -- it will become a member
                value = value.value
            non_auto_store = True
            single = False
            if isinstance(value, auto):
                single = True
                value = (value, )
            if isinstance(value, tuple) and any(isinstance(v, auto) for v in value):
                # insist on an actual tuple, no subclasses, in keeping with only supporting
                # top-level auto() usage (not contained in any other data structure)
                auto_valued = []
                t = type(value)
                for v in value:
                    if isinstance(v, auto):
                        non_auto_store = False
                        if v.value == _auto_null:
                            v.value = self._generate_next_value(
                                    key, 1, len(self._member_names), self._last_values[:],
                                    )
                            self._auto_called = True
                        v = v.value
                        self._last_values.append(v)
                    auto_valued.append(v)
                if single:
                    value = auto_valued[0]
                else:
                    try:
                        # accepts iterable as multiple arguments?
                        value = t(auto_valued)
                    except TypeError:
                        # then pass them in singly
                        value = t(*auto_valued)
            self._member_names[key] = None
            if non_auto_store:
                self._last_values.append(value)
        super().__setitem__(key, value)

    @property
    def member_names(self):
        return list(self._member_names)

    def update(self, members, **more_members):
        try:
            for name in members.keys():
                self[name] = members[name]
        except AttributeError:
            for name, value in members:
                self[name] = value
        for name, value in more_members.items():
            self[name] = value

_EnumDict = EnumDict        # keep private name for backwards compatibility


class EnumType(type):
    """
    Metaclass for Enum
    """

    @classmethod
    def __prepare__(metacls, cls, bases, **kwds):
        # check that previous enum members do not exist
        metacls._check_for_existing_members_(cls, bases)
        # create the namespace dict
        enum_dict = EnumDict(cls)
        # inherit previous flags and _generate_next_value_ function
        member_type, first_enum = metacls._get_mixins_(cls, bases)
        if first_enum is not None:
            enum_dict['_generate_next_value_'] = getattr(
                    first_enum, '_generate_next_value_', None,
                    )
        return enum_dict

    def __new__(metacls, cls, bases, classdict, *, boundary=None, _simple=False, **kwds):
        # an Enum class is final once enumeration items have been defined; it
        # cannot be mixed with other types (int, float, etc.) if it has an
        # inherited __new__ unless a new __new__ is defined (or the resulting
        # class will fail).
        #
        if _simple:
            return super().__new__(metacls, cls, bases, classdict, **kwds)
        #
        # remove any keys listed in _ignore_
        classdict.setdefault('_ignore_', []).append('_ignore_')
        ignore = classdict['_ignore_']
        for key in ignore:
            classdict.pop(key, None)
        #
        # grab member names
        member_names = classdict._member_names
        #
        # check for illegal enum names (any others?)
        invalid_names = set(member_names) & {'mro', ''}
        if invalid_names:
            raise ValueError('invalid enum member name(s) %s'  % (
                    ','.join(repr(n) for n in invalid_names)
                    ))
        #
        # adjust the sunders
        _order_ = classdict.pop('_order_', None)
        _gnv = classdict.get('_generate_next_value_')
        if _gnv is not None and type(_gnv) is not staticmethod:
            _gnv = staticmethod(_gnv)
        # convert to normal dict
        classdict = dict(classdict.items())
        if _gnv is not None:
            classdict['_generate_next_value_'] = _gnv
        #
        # data type of member and the controlling Enum class
        member_type, first_enum = metacls._get_mixins_(cls, bases)
        __new__, save_new, use_args = metacls._find_new_(
                classdict, member_type, first_enum,
                )
        classdict['_new_member_'] = __new__
        classdict['_use_args_'] = use_args
        #
        # convert future enum members into temporary _proto_members
        for name in member_names:
            value = classdict[name]
            classdict[name] = _proto_member(value)
        #
        # house-keeping structures
        classdict['_member_names_'] = []
        classdict['_member_map_'] = {}
        classdict['_value2member_map_'] = {}
        classdict['_hashable_values_'] = []          # for comparing with non-hashable types
        classdict['_unhashable_values_'] = []       # e.g. frozenset() with set()
        classdict['_unhashable_values_map_'] = {}
        classdict['_member_type_'] = member_type
        # now set the __repr__ for the value
        classdict['_value_repr_'] = metacls._find_data_repr_(cls, bases)
        #
        # Flag structures (will be removed if final class is not a Flag
        classdict['_boundary_'] = (
                boundary
                or getattr(first_enum, '_boundary_', None)
                )
        classdict['_flag_mask_'] = 0
        classdict['_singles_mask_'] = 0
        classdict['_all_bits_'] = 0
        classdict['_inverted_'] = None
        try:
            classdict['_%s__in_progress' % cls] = True
            enum_class = super().__new__(metacls, cls, bases, classdict, **kwds)
            classdict['_%s__in_progress' % cls] = False
            delattr(enum_class, '_%s__in_progress' % cls)
        except Exception as e:
            # since 3.12 the note "Error calling __set_name__ on '_proto_member' instance ..."
            # is tacked on to the error instead of raising a RuntimeError, so discard it
            if hasattr(e, '__notes__'):
                del e.__notes__
            raise
        # update classdict with any changes made by __init_subclass__
        classdict.update(enum_class.__dict__)
        #
        # double check that repr and friends are not the mixin's or various
        # things break (such as pickle)
        # however, if the method is defined in the Enum itself, don't replace
        # it
        #
        # Also, special handling for ReprEnum
        if ReprEnum is not None and ReprEnum in bases:
            if member_type is object:
                raise TypeError(
                        'ReprEnum subclasses must be mixed with a data type (i.e.'
                        ' int, str, float, etc.)'
                        )
            if '__format__' not in classdict:
                enum_class.__format__ = member_type.__format__
                classdict['__format__'] = enum_class.__format__
            if '__str__' not in classdict:
                method = member_type.__str__
                if method is object.__str__:
                    # if member_type does not define __str__, object.__str__ will use
                    # its __repr__ instead, so we'll also use its __repr__
                    method = member_type.__repr__
                enum_class.__str__ = method
                classdict['__str__'] = enum_class.__str__
        for name in ('__repr__', '__str__', '__format__', '__reduce_ex__'):
            if name not in classdict:
                # check for mixin overrides before replacing
                enum_method = getattr(first_enum, name)
                found_method = getattr(enum_class, name)
                object_method = getattr(object, name)
                data_type_method = getattr(member_type, name)
                if found_method in (data_type_method, object_method):
                    setattr(enum_class, name, enum_method)
        #
        # for Flag, add __or__, __and__, __xor__, and __invert__
        if Flag is not None and issubclass(enum_class, Flag):
            for name in (
                    '__or__', '__and__', '__xor__',
                    '__ror__', '__rand__', '__rxor__',
                    '__invert__'
                ):
                if name not in classdict:
                    enum_method = getattr(Flag, name)
                    setattr(enum_class, name, enum_method)
                    classdict[name] = enum_method
        #
        # replace any other __new__ with our own (as long as Enum is not None,
        # anyway) -- again, this is to support pickle
        if Enum is not None:
            # if the user defined their own __new__, save it before it gets
            # clobbered in case they subclass later
            if save_new:
                enum_class.__new_member__ = __new__
            enum_class.__new__ = Enum.__new__
        #
        # py3 support for definition order (helps keep py2/py3 code in sync)
        #
        # _order_ checking is spread out into three/four steps
        # - if enum_class is a Flag:
        #   - remove any non-single-bit flags from _order_
        # - remove any aliases from _order_
        # - check that _order_ and _member_names_ match
        #
        # step 1: ensure we have a list
        if _order_ is not None:
            if isinstance(_order_, str):
                _order_ = _order_.replace(',', ' ').split()
        #
        # remove Flag structures if final class is not a Flag
        if (
                Flag is None and cls != 'Flag'
                or Flag is not None and not issubclass(enum_class, Flag)
            ):
            delattr(enum_class, '_boundary_')
            delattr(enum_class, '_flag_mask_')
            delattr(enum_class, '_singles_mask_')
            delattr(enum_class, '_all_bits_')
            delattr(enum_class, '_inverted_')
        elif Flag is not None and issubclass(enum_class, Flag):
            # set correct __iter__
            member_list = [m._value_ for m in enum_class]
            if member_list != sorted(member_list):
                enum_class._iter_member_ = enum_class._iter_member_by_def_
            if _order_:
                # _order_ step 2: remove any items from _order_ that are not single-bit
                _order_ = [
                        o
                        for o in _order_
                        if o not in enum_class._member_map_ or _is_single_bit(enum_class[o]._value_)
                        ]
        #
        if _order_:
            # _order_ step 3: remove aliases from _order_
            _order_ = [
                    o
                    for o in _order_
                    if (
                        o not in enum_class._member_map_
                        or
                        (o in enum_class._member_map_ and o in enum_class._member_names_)
                        )]
            # _order_ step 4: verify that _order_ and _member_names_ match
            if _order_ != enum_class._member_names_:
                raise TypeError(
                        'member order does not match _order_:\n  %r\n  %r'
                        % (enum_class._member_names_, _order_)
                        )
        #
        return enum_class

    def __bool__(cls):
        """
        classes/types should always be True.
        """
        return True

    def __call__(cls, value, names=_not_given, *values, module=None, qualname=None, type=None, start=1, boundary=None):
        """
        Either returns an existing member, or creates a new enum class.

        This method is used both when an enum class is given a value to match
        to an enumeration member (i.e. Color(3)) and for the functional API
        (i.e. Color = Enum('Color', names='RED GREEN BLUE')).

        The value lookup branch is chosen if the enum is final.

        When used for the functional API:

        `value` will be the name of the new class.

        `names` should be either a string of white-space/comma delimited names
        (values will start at `start`), or an iterator/mapping of name, value pairs.

        `module` should be set to the module this class is being created in;
        if it is not set, an attempt to find that module will be made, but if
        it fails the class will not be picklable.

        `qualname` should be set to the actual location this class can be found
        at in its module; by default it is set to the global scope.  If this is
        not correct, unpickling will fail in some circumstances.

        `type`, if set, will be mixed in as the first base class.
        """
        if cls._member_map_:
            # simple value lookup if members exist
            if names is not _not_given:
                value = (value, names) + values
            return cls.__new__(cls, value)
        # otherwise, functional API: we're creating a new Enum type
        if names is _not_given and type is None:
            # no body? no data-type? possibly wrong usage
            raise TypeError(
                    f"{cls} has no members; specify `names=()` if you meant to create a new, empty, enum"
                    )
        return cls._create_(
                class_name=value,
                names=None if names is _not_given else names,
                module=module,
                qualname=qualname,
                type=type,
                start=start,
                boundary=boundary,
                )

    def __contains__(cls, value):
        """Return True if `value` is in `cls`.

        `value` is in `cls` if:
        1) `value` is a member of `cls`, or
        2) `value` is the value of one of the `cls`'s members.
        3) `value` is a pseudo-member (flags)
        """
        if isinstance(value, cls):
            return True
        if issubclass(cls, Flag):
            try:
                result = cls._missing_(value)
                return isinstance(result, cls)
            except ValueError:
                pass
        return (
                value in cls._unhashable_values_    # both structures are lists
                or value in cls._hashable_values_
                )

    def __delattr__(cls, attr):
        # nicer error message when someone tries to delete an attribute
        # (see issue19025).
        if attr in cls._member_map_:
            raise AttributeError("%r cannot delete member %r." % (cls.__name__, attr))
        super().__delattr__(attr)

    def __dir__(cls):
        interesting = set([
                '__class__', '__contains__', '__doc__', '__getitem__',
                '__iter__', '__len__', '__members__', '__module__',
                '__name__', '__qualname__',
                ]
                + cls._member_names_
                )
        if cls._new_member_ is not object.__new__:
            interesting.add('__new__')
        if cls.__init_subclass__ is not object.__init_subclass__:
            interesting.add('__init_subclass__')
        if cls._member_type_ is object:
            return sorted(interesting)
        else:
            # return whatever mixed-in data type has
            return sorted(set(dir(cls._member_type_)) | interesting)

    def __getitem__(cls, name):
        """
        Return the member matching `name`.
        """
        return cls._member_map_[name]

    def __iter__(cls):
        """
        Return members in definition order.
        """
        return (cls._member_map_[name] for name in cls._member_names_)

    def __len__(cls):
        """
        Return the number of members (no aliases)
        """
        return len(cls._member_names_)

    @bltns.property
    def __members__(cls):
        """
        Returns a mapping of member name->value.

        This mapping lists all enum members, including aliases. Note that this
        is a read-only view of the internal mapping.
        """
        return MappingProxyType(cls._member_map_)

    def __repr__(cls):
        if Flag is not None and issubclass(cls, Flag):
            return "<flag %r>" % cls.__name__
        else:
            return "<enum %r>" % cls.__name__

    def __reversed__(cls):
        """
        Return members in reverse definition order.
        """
        return (cls._member_map_[name] for name in reversed(cls._member_names_))

    def __setattr__(cls, name, value):
        """
        Block attempts to reassign Enum members.

        A simple assignment to the class namespace only changes one of the
        several possible ways to get an Enum member from the Enum class,
        resulting in an inconsistent Enumeration.
        """
        member_map = cls.__dict__.get('_member_map_', {})
        if name in member_map:
            raise AttributeError('cannot reassign member %r' % (name, ))
        super().__setattr__(name, value)

    def _create_(cls, class_name, names, *, module=None, qualname=None, type=None, start=1, boundary=None):
        """
        Convenience method to create a new Enum class.

        `names` can be:

        * A string containing member names, separated either with spaces or
          commas.  Values are incremented by 1 from `start`.
        * An iterable of member names.  Values are incremented by 1 from `start`.
        * An iterable of (member name, value) pairs.
        * A mapping of member name -> value pairs.
        """
        metacls = cls.__class__
        bases = (cls, ) if type is None else (type, cls)
        _, first_enum = cls._get_mixins_(class_name, bases)
        classdict = metacls.__prepare__(class_name, bases)

        # special processing needed for names?
        if isinstance(names, str):
            names = names.replace(',', ' ').split()
        if isinstance(names, (tuple, list)) and names and isinstance(names[0], str):
            original_names, names = names, []
            last_values = []
            for count, name in enumerate(original_names):
                value = first_enum._generate_next_value_(name, start, count, last_values[:])
                last_values.append(value)
                names.append((name, value))
        if names is None:
            names = ()

        # Here, names is either an iterable of (name, value) or a mapping.
        for item in names:
            if isinstance(item, str):
                member_name, member_value = item, names[item]
            else:
                member_name, member_value = item
            classdict[member_name] = member_value

        if module is None:
            try:
                module = sys._getframemodulename(2)
            except AttributeError:
                # Fall back on _getframe if _getframemodulename is missing
                try:
                    module = sys._getframe(2).f_globals['__name__']
                except (AttributeError, ValueError, KeyError):
                    pass
        if module is None:
            _make_class_unpicklable(classdict)
        else:
            classdict['__module__'] = module
        if qualname is not None:
            classdict['__qualname__'] = qualname

        return metacls.__new__(metacls, class_name, bases, classdict, boundary=boundary)

    def _convert_(cls, name, module, filter, source=None, *, boundary=None, as_global=False):
        """
        Create a new Enum subclass that replaces a collection of global constants
        """
        # convert all constants from source (or module) that pass filter() to
        # a new Enum called name, and export the enum and its members back to
        # module;
        # also, replace the __reduce_ex__ method so unpickling works in
        # previous Python versions
        module_globals = sys.modules[module].__dict__
        if source:
            source = source.__dict__
        else:
            source = module_globals
        # _value2member_map_ is populated in the same order every time
        # for a consistent reverse mapping of number to name when there
        # are multiple names for the same number.
        members = [
                (name, value)
                for name, value in source.items()
                if filter(name)]
        try:
            # sort by value
            members.sort(key=lambda t: (t[1], t[0]))
        except TypeError:
            # unless some values aren't comparable, in which case sort by name
            members.sort(key=lambda t: t[0])
        body = {t[0]: t[1] for t in members}
        body['__module__'] = module
        tmp_cls = type(name, (object, ), body)
        cls = _simple_enum(etype=cls, boundary=boundary or KEEP)(tmp_cls)
        if as_global:
            global_enum(cls)
        else:
            sys.modules[cls.__module__].__dict__.update(cls.__members__)
        module_globals[name] = cls
        return cls

    @classmethod
    def _check_for_existing_members_(mcls, class_name, bases):
        for chain in bases:
            for base in chain.__mro__:
                if isinstance(base, EnumType) and base._member_names_:
                    raise TypeError(
                            "<enum %r> cannot extend %r"
                            % (class_name, base)
                            )

    @classmethod
    def _get_mixins_(mcls, class_name, bases):
        """
        Returns the type for creating enum members, and the first inherited
        enum class.

        bases: the tuple of bases that was given to __new__
        """
        if not bases:
            return object, Enum
        # ensure final parent class is an Enum derivative, find any concrete
        # data type, and check that Enum has no members
        first_enum = bases[-1]
        if not isinstance(first_enum, EnumType):
            raise TypeError("new enumerations should be created as "
                    "`EnumName([mixin_type, ...] [data_type,] enum_type)`")
        member_type = mcls._find_data_type_(class_name, bases) or object
        return member_type, first_enum

    @classmethod
    def _find_data_repr_(mcls, class_name, bases):
        for chain in bases:
            for base in chain.__mro__:
                if base is object:
                    continue
                elif isinstance(base, EnumType):
                    # if we hit an Enum, use it's _value_repr_
                    return base._value_repr_
                elif '__repr__' in base.__dict__:
                    # this is our data repr
                    # double-check if a dataclass with a default __repr__
                    if (
                            '__dataclass_fields__' in base.__dict__
                            and '__dataclass_params__' in base.__dict__
                            and base.__dict__['__dataclass_params__'].repr
                        ):
                        return _dataclass_repr
                    else:
                        return base.__dict__['__repr__']
        return None

    @classmethod
    def _find_data_type_(mcls, class_name, bases):
        # a datatype has a __new__ method, or a __dataclass_fields__ attribute
        data_types = set()
        base_chain = set()
        for chain in bases:
            candidate = None
            for base in chain.__mro__:
                base_chain.add(base)
                if base is object:
                    continue
                elif isinstance(base, EnumType):
                    if base._member_type_ is not object:
                        data_types.add(base._member_type_)