| import sys |
| from collections import OrderedDict |
| from types import MappingProxyType |
| |
| __all__ = ['Enum', 'IntEnum', 'unique'] |
| |
| |
| class _RouteClassAttributeToGetattr: |
| """Route attribute access on a class to __getattr__. |
| |
| This is a descriptor, used to define attributes that act differently when |
| accessed through an instance and through a class. Instance access remains |
| normal, but access to an attribute through a class will be routed to the |
| class's __getattr__ method; this is done by raising AttributeError. |
| |
| """ |
| def __init__(self, fget=None): |
| self.fget = fget |
| |
| def __get__(self, instance, ownerclass=None): |
| if instance is None: |
| raise AttributeError() |
| return self.fget(instance) |
| |
| def __set__(self, instance, value): |
| raise AttributeError("can't set attribute") |
| |
| def __delete__(self, instance): |
| raise AttributeError("can't delete attribute") |
| |
| |
| def _is_dunder(name): |
| """Returns True if a __dunder__ name, False otherwise.""" |
| return (name[:2] == name[-2:] == '__' and |
| name[2:3] != '_' and |
| name[-3:-2] != '_') |
| |
| |
| def _is_sunder(name): |
| """Returns True if a _sunder_ name, False otherwise.""" |
| return (name[0] == name[-1] == '_' and |
| name[1:2] != '_' and |
| name[-2:-1] != '_') |
| |
| |
| def _make_class_unpicklable(cls): |
| """Make the given class un-picklable.""" |
| def _break_on_call_reduce(self): |
| raise TypeError('%r cannot be pickled' % self) |
| cls.__reduce__ = _break_on_call_reduce |
| cls.__module__ = '<unknown>' |
| |
| |
| class _EnumDict(dict): |
| """Keeps track of definition order of the enum items. |
| |
| EnumMeta will use the names found in self._member_names as the |
| enumeration member names. |
| |
| """ |
| def __init__(self): |
| super().__init__() |
| self._member_names = [] |
| |
| def __setitem__(self, key, value): |
| """Changes anything not dundered or that doesn't have __get__. |
| |
| If a descriptor is added with the same name as an enum member, the name |
| is removed from _member_names (this may leave a hole in the numerical |
| sequence of values). |
| |
| 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 _is_sunder(key): |
| raise ValueError('_names_ are reserved for future Enum use') |
| elif _is_dunder(key) or hasattr(value, '__get__'): |
| if key in self._member_names: |
| # overwriting an enum with a method? then remove the name from |
| # _member_names or it will become an enum anyway when the class |
| # is created |
| self._member_names.remove(key) |
| else: |
| if key in self._member_names: |
| raise TypeError('Attempted to reuse key: %r' % key) |
| self._member_names.append(key) |
| super().__setitem__(key, value) |
| |
| |
| # Dummy value for Enum as EnumMeta explicity checks for it, but of course until |
| # EnumMeta finishes running the first time the Enum class doesn't exist. This |
| # is also why there are checks in EnumMeta like `if Enum is not None` |
| Enum = None |
| |
| |
| class EnumMeta(type): |
| """Metaclass for Enum""" |
| @classmethod |
| def __prepare__(metacls, cls, bases): |
| return _EnumDict() |
| |
| def __new__(metacls, cls, bases, classdict): |
| # 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). |
| member_type, first_enum = metacls._get_mixins_(bases) |
| __new__, save_new, use_args = metacls._find_new_(classdict, member_type, |
| first_enum) |
| |
| # save enum items into separate mapping so they don't get baked into |
| # the new class |
| members = {k: classdict[k] for k in classdict._member_names} |
| for name in classdict._member_names: |
| del classdict[name] |
| |
| # check for illegal enum names (any others?) |
| invalid_names = set(members) & {'mro', } |
| if invalid_names: |
| raise ValueError('Invalid enum member name: {0}'.format( |
| ','.join(invalid_names))) |
| |
| # create our new Enum type |
| enum_class = super().__new__(metacls, cls, bases, classdict) |
| enum_class._member_names_ = [] # names in definition order |
| enum_class._member_map_ = OrderedDict() # name->value map |
| enum_class._member_type_ = member_type |
| |
| # Reverse value->name map for hashable values. |
| enum_class._value2member_map_ = {} |
| |
| # check for a __getnewargs__, and if not present sabotage |
| # pickling, since it won't work anyway |
| if (member_type is not object and |
| member_type.__dict__.get('__getnewargs__') is None |
| ): |
| _make_class_unpicklable(enum_class) |
| |
| # instantiate them, checking for duplicates as we go |
| # we instantiate first instead of checking for duplicates first in case |
| # a custom __new__ is doing something funky with the values -- such as |
| # auto-numbering ;) |
| for member_name in classdict._member_names: |
| value = members[member_name] |
| if not isinstance(value, tuple): |
| args = (value, ) |
| else: |
| args = value |
| if member_type is tuple: # special case for tuple enums |
| args = (args, ) # wrap it one more time |
| if not use_args: |
| enum_member = __new__(enum_class) |
| if not hasattr(enum_member, '_value_'): |
| enum_member._value_ = value |
| else: |
| enum_member = __new__(enum_class, *args) |
| if not hasattr(enum_member, '_value_'): |
| enum_member._value_ = member_type(*args) |
| value = enum_member._value_ |
| enum_member._name_ = member_name |
| enum_member.__init__(*args) |
| # If another member with the same value was already defined, the |
| # new member becomes an alias to the existing one. |
| for name, canonical_member in enum_class._member_map_.items(): |
| if canonical_member.value == enum_member._value_: |
| enum_member = canonical_member |
| break |
| else: |
| # Aliases don't appear in member names (only in __members__). |
| enum_class._member_names_.append(member_name) |
| enum_class._member_map_[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_[value] = enum_member |
| except TypeError: |
| pass |
| |
| # double check that repr and friends are not the mixin's or various |
| # things break (such as pickle) |
| for name in ('__repr__', '__str__', '__getnewargs__'): |
| class_method = getattr(enum_class, name) |
| obj_method = getattr(member_type, name, None) |
| enum_method = getattr(first_enum, name, None) |
| if obj_method is not None and obj_method is class_method: |
| setattr(enum_class, 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__ |
| return enum_class |
| |
| def __call__(cls, value, names=None, *, module=None, type=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')). |
| |
| When used for the functional API: `module`, if set, will be stored in |
| the new class' __module__ attribute; `type`, if set, will be mixed in |
| as the first base class. |
| |
| Note: if `module` is not set this routine will attempt to discover the |
| calling module by walking the frame stack; if this is unsuccessful |
| the resulting class will not be pickleable. |
| |
| """ |
| if names is None: # simple value lookup |
| return cls.__new__(cls, value) |
| # otherwise, functional API: we're creating a new Enum type |
| return cls._create_(value, names, module=module, type=type) |
| |
| def __contains__(cls, member): |
| return isinstance(member, cls) and member.name in cls._member_map_ |
| |
| def __dir__(self): |
| return ['__class__', '__doc__', '__members__'] + self._member_names_ |
| |
| @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 __getattr__(cls, name): |
| """Return the enum member matching `name` |
| |
| We use __getattr__ instead of descriptors or inserting into the enum |
| class' __dict__ in order to support `name` and `value` being both |
| properties for enum members (which live in the class' __dict__) and |
| enum members themselves. |
| |
| """ |
| if _is_dunder(name): |
| raise AttributeError(name) |
| try: |
| return cls._member_map_[name] |
| except KeyError: |
| raise AttributeError(name) from None |
| |
| def __getitem__(cls, name): |
| return cls._member_map_[name] |
| |
| def __iter__(cls): |
| return (cls._member_map_[name] for name in cls._member_names_) |
| |
| def __len__(cls): |
| return len(cls._member_names_) |
| |
| def __repr__(cls): |
| return "<enum %r>" % cls.__name__ |
| |
| def _create_(cls, class_name, names=None, *, module=None, type=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 auto-numbered from 1. |
| * An iterable of member names. Values are auto-numbered from 1. |
| * An iterable of (member name, value) pairs. |
| * A mapping of member name -> value. |
| |
| """ |
| metacls = cls.__class__ |
| bases = (cls, ) if type is None else (type, cls) |
| 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 isinstance(names[0], str): |
| names = [(e, i) for (i, e) in enumerate(names, 1)] |
| |
| # 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 |
| enum_class = metacls.__new__(metacls, class_name, bases, classdict) |
| |
| # TODO: replace the frame hack if a blessed way to know the calling |
| # module is ever developed |
| if module is None: |
| try: |
| module = sys._getframe(2).f_globals['__name__'] |
| except (AttributeError, ValueError) as exc: |
| pass |
| if module is None: |
| _make_class_unpicklable(enum_class) |
| else: |
| enum_class.__module__ = module |
| |
| return enum_class |
| |
| @staticmethod |
| def _get_mixins_(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 |
| |
| # double check that we are not subclassing a class with existing |
| # enumeration members; while we're at it, see if any other data |
| # type has been mixed in so we can use the correct __new__ |
| member_type = first_enum = None |
| for base in bases: |
| if (base is not Enum and |
| issubclass(base, Enum) and |
| base._member_names_): |
| raise TypeError("Cannot extend enumerations") |
| # base is now the last base in bases |
| if not issubclass(base, Enum): |
| raise TypeError("new enumerations must be created as " |
| "`ClassName([mixin_type,] enum_type)`") |
| |
| # get correct mix-in type (either mix-in type of Enum subclass, or |
| # first base if last base is Enum) |
| if not issubclass(bases[0], Enum): |
| member_type = bases[0] # first data type |
| first_enum = bases[-1] # enum type |
| else: |
| for base in bases[0].__mro__: |
| # most common: (IntEnum, int, Enum, object) |
| # possible: (<Enum 'AutoIntEnum'>, <Enum 'IntEnum'>, |
| # <class 'int'>, <Enum 'Enum'>, |
| # <class 'object'>) |
| if issubclass(base, Enum): |
| if first_enum is None: |
| first_enum = base |
| else: |
| if member_type is None: |
| member_type = base |
| |
| return member_type, first_enum |
| |
| @staticmethod |
| def _find_new_(classdict, member_type, first_enum): |
| """Returns the __new__ to be used for creating the enum members. |
| |
| classdict: the class dictionary given to __new__ |
| member_type: the data type whose __new__ will be used by default |
| first_enum: enumeration to check for an overriding __new__ |
| |
| """ |
| # now find the correct __new__, checking to see of one was defined |
| # by the user; also check earlier enum classes in case a __new__ was |
| # saved as __new_member__ |
| __new__ = classdict.get('__new__', None) |
| |
| # should __new__ be saved as __new_member__ later? |
| save_new = __new__ is not None |
| |
| if __new__ is None: |
| # check all possibles for __new_member__ before falling back to |
| # __new__ |
| for method in ('__new_member__', '__new__'): |
| for possible in (member_type, first_enum): |
| target = getattr(possible, method, None) |
| if target not in { |
| None, |
| None.__new__, |
| object.__new__, |
| Enum.__new__, |
| }: |
| __new__ = target |
| break |
| if __new__ is not None: |
| break |
| else: |
| __new__ = object.__new__ |
| |
| # if a non-object.__new__ is used then whatever value/tuple was |
| # assigned to the enum member name will be passed to __new__ and to the |
| # new enum member's __init__ |
| if __new__ is object.__new__: |
| use_args = False |
| else: |
| use_args = True |
| |
| return __new__, save_new, use_args |
| |
| |
| class Enum(metaclass=EnumMeta): |
| """Generic enumeration. |
| |
| Derive from this class to define new enumerations. |
| |
| """ |
| def __new__(cls, value): |
| # all enum instances are actually created during class construction |
| # without calling this method; this method is called by the metaclass' |
| # __call__ (i.e. Color(3) ), and by pickle |
| if type(value) is cls: |
| # For lookups like Color(Color.red) |
| return value |
| # by-value search for a matching enum member |
| # see if it's in the reverse mapping (for hashable values) |
| try: |
| if value in cls._value2member_map_: |
| return cls._value2member_map_[value] |
| except TypeError: |
| # not there, now do long search -- O(n) behavior |
| for member in cls._member_map_.values(): |
| if member.value == value: |
| return member |
| raise ValueError("%s is not a valid %s" % (value, cls.__name__)) |
| |
| def __repr__(self): |
| return "<%s.%s: %r>" % ( |
| self.__class__.__name__, self._name_, self._value_) |
| |
| def __str__(self): |
| return "%s.%s" % (self.__class__.__name__, self._name_) |
| |
| def __dir__(self): |
| return (['__class__', '__doc__', 'name', 'value']) |
| |
| def __eq__(self, other): |
| if type(other) is self.__class__: |
| return self is other |
| return NotImplemented |
| |
| def __getnewargs__(self): |
| return (self._value_, ) |
| |
| def __hash__(self): |
| return hash(self._name_) |
| |
| # _RouteClassAttributeToGetattr is used to provide access to the `name` |
| # and `value` properties of enum members while keeping some measure of |
| # protection from modification, while still allowing for an enumeration |
| # to have members named `name` and `value`. This works because enumeration |
| # members are not set directly on the enum class -- __getattr__ is |
| # used to look them up. |
| |
| @_RouteClassAttributeToGetattr |
| def name(self): |
| return self._name_ |
| |
| @_RouteClassAttributeToGetattr |
| def value(self): |
| return self._value_ |
| |
| |
| class IntEnum(int, Enum): |
| """Enum where members are also (and must be) ints""" |
| |
| |
| def unique(enumeration): |
| """Class decorator for enumerations ensuring unique member values.""" |
| duplicates = [] |
| for name, member in enumeration.__members__.items(): |
| if name != member.name: |
| duplicates.append((name, member.name)) |
| if duplicates: |
| alias_details = ', '.join( |
| ["%s -> %s" % (alias, name) for (alias, name) in duplicates]) |
| raise ValueError('duplicate values found in %r: %s' % |
| (enumeration, alias_details)) |
| return enumeration |