"""Python Enumerations"""
import sys as _sys
__all__ = ['Enum', 'IntEnum', 'unique']
version = 1, 0, 4
pyver = float('%s.%s' % _sys.version_info[:2])
try:
any
except NameError:
def any(iterable):
for element in iterable:
if element:
return True
return False
try:
from collections import OrderedDict
except ImportError:
OrderedDict = None
try:
basestring
except NameError:
# In Python 2 basestring is the ancestor of both str and unicode
# in Python 3 it's just str, but was missing in 3.1
basestring = str
try:
unicode
except NameError:
# In Python 3 unicode no longer exists (it's just str)
unicode = str
class _RouteClassAttributeToGetattr(object):
"""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_descriptor(obj):
"""Returns True if obj is a descriptor, False otherwise."""
return (
hasattr(obj, '__get__') or
hasattr(obj, '__set__') or
hasattr(obj, '__delete__'))
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] != '_' and
len(name) > 4)
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] != '_' and
len(name) > 2)
def _make_class_unpicklable(cls):
"""Make the given class un-picklable."""
def _break_on_call_reduce(self, protocol=None):
raise TypeError('%r cannot be pickled' % self)
cls.__reduce_ex__ = _break_on_call_reduce
cls.__module__ = '<unknown>'
class _EnumDict(dict):
"""Track enum member order and ensure member names are not reused.
EnumMeta will use the names found in self._member_names as the
enumeration member names.
"""
def __init__(self):
super(_EnumDict, self).__init__()
self._member_names = []
def __setitem__(self, key, value):
"""Changes anything not dundered or not a descriptor.
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.
Note: in 3.x __order__ is simply discarded as a not necessary piece
leftover from 2.x
"""
if pyver >= 3.0 and key == '__order__':
return
if _is_sunder(key):
raise ValueError('_names_ are reserved for future Enum use')
elif _is_dunder(key):
pass
elif key in self._member_names:
# descriptor overwriting an enum?
raise TypeError('Attempted to reuse key: %r' % key)
elif not _is_descriptor(value):
if key in self:
# enum overwriting a descriptor?
raise TypeError('Key already defined as: %r' % self[key])
self._member_names.append(key)
super(_EnumDict, self).__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).
if type(classdict) is dict:
original_dict = classdict
classdict = _EnumDict()
for k, v in original_dict.items():
classdict[k] = v
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 = dict((k, classdict[k]) for k in classdict._member_names)
for name in classdict._member_names:
del classdict[name]
# py2 support for definition order
__order__ = classdict.get('__order__')
if __order__ is None:
if pyver < 3.0:
try:
__order__ = [name for (name, value) in sorted(members.items(), key=lambda item: item[1])]
except TypeError:
__order__ = [name for name in sorted(members.keys())]
else:
__order__ = classdict._member_names
else:
del classdict['__order__']
if pyver < 3.0:
__order__ = __order__.replace(',', ' ').split()
aliases = [name for name in members if name not in __order__]
__order__ += aliases
# check for illegal enum names (any others?)
invalid_names = set(members) & set(['mro'])
if invalid_names:
raise ValueError('Invalid enum member name(s): %s' % (
', '.join(invalid_names), ))
# create our new Enum type
enum_class = super(EnumMeta, metacls).__new__(metacls, cls, bases, classdict)
enum_class._member_names_ = [] # names in random order
if OrderedDict is not None:
enum_class._member_map_ = OrderedDict()
else:
enum_class._member_map_ = {} # name->value map
enum_class._member_type_ = member_type
# Reverse value->name map for hashable values.
enum_class._value2member_map_ = {}
# 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 ;)
if __new__ is None:
__new__ = enum_class.__new__
for member_name in __order__:
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 or not 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.__objclass__ = enum_class
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
# If a custom type is mixed into the Enum, and it does not know how
# to pickle itself, pickle.dumps will succeed but pickle.loads will
# fail. Rather than have the error show up later and possibly far
# from the source, sabotage the pickle protocol for this class so
# that pickle.dumps also fails.
#
# However, if the new class implements its own __reduce_ex__, do not
# sabotage -- it's on them to make sure it works correctly. We use
# __reduce_ex__ instead of any of the others as it is preferred by
# pickle over __reduce__, and it handles all pickle protocols.
unpicklable = False
if '__reduce_ex__' not in classdict:
if member_type is not object:
methods = ('__getnewargs_ex__', '__getnewargs__',
'__reduce_ex__', '__reduce__')
if not any(m in member_type.__dict__ for m in methods):
_make_class_unpicklable(enum_class)
unpicklable = True
# double check that repr and friends are not the mixin's or various
# things break (such as pickle)
for name in ('__repr__', '__str__', '__format__', '__reduce_ex__'):
class_method = getattr(enum_class, name)
obj_method = getattr(member_type, name, None)
enum_method = getattr(first_enum, name, None)
if name not in classdict and class_method is not enum_method:
if name == '__reduce_ex__' and unpicklable:
continue
setattr(enum_class, name, enum_method)
# method resolution and int's are not playing nice
# Python's less than 2.6 use __cmp__
if pyver < 2.6:
if issubclass(enum_class, int):
setattr(enum_class, '__cmp__', getattr(int, '__cmp__'))
elif pyver < 3.0:
if issubclass(enum_class, int):
for method in (
'__le__',
'__lt__',
'__gt__',
'__ge__',
'__eq__',
'__ne__',
'__hash__',
):
setattr(enum_class, method, getattr(int, 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:
setattr(enum_class, '__member_new__', enum_class.__dict__['__new__'])
setattr(enum_class, '__new__', Enum.__dict__['__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 __delattr__(cls, attr):
# nicer error message when someone tries to delete an attribute
# (see issue19025).
if attr in cls._member_map_:
raise AttributeError(
"%s: cannot delete Enum member." % cls.__name__)
super(EnumMeta, cls).__delattr__(attr)
def __dir__(self):
return (['__class__', '__doc__', '__members__', '__module__'] +
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 copy of the internal mapping.
"""
return cls._member_map_.copy()
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)
def __getitem__(cls, name):
return cls._member_map_[name]
def __iter__(cls):
return (cls._member_map_[name] for name in cls._member_names_)
def __reversed__(cls):
return (cls._member_map_[name] for name in reversed(cls._member_names_))
def __len__(cls):
return len(cls._member_names_)
def __repr__(cls):
return "<enum %r>" % cls.__name__
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 members.')
super(EnumMeta, cls).__setattr__(name, value)
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.
"""
if pyver < 3.0:
# if class_name is unicode, attempt a conversion to ASCII
if isinstance(class_name, unicode):
try:
class_name = class_name.encode('ascii')
except UnicodeEncodeError:
raise TypeError('%r is not representable in ASCII' % class_name)
metacls = cls.__class__
if type is None:
bases = (cls, )
else:
bases = (type, cls)
classdict = metacls.__prepare__(class_name, bases)
__order__ = []
# special processing needed for names?
if isinstance(names, basestring):
names = names.replace(',', ' ').split()
if isinstance(names, (tuple, list)) and isinstance(names[0], basestring):
names = [(e, i+1) for (i, e) in enumerate(names)]
# Here, names is either an iterable of (name, value) or a mapping.
for item in names:
if isinstance(item, basestring):
member_name, member_value = item, names[item]
else:
member_name, member_value = item
classdict[member_name] = member_value
__order__.append(member_name)
# only set __order__ in classdict if name/value was not from a mapping
if not isinstance(item, basestring):
classdict['__order__'] = ' '.join(__order__)
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):
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 or Enum is None:
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
if pyver < 3.0:
@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 __member_new__
__new__ = classdict.get('__new__', None)
if __new__:
return None, True, True # __new__, save_new, use_args
N__new__ = getattr(None, '__new__')
O__new__ = getattr(object, '__new__')
if Enum is None:
E__new__ = N__new__
else:
E__new__ = Enum.__dict__['__new__']
# check all possibles for __member_new__ before falling back to
# __new__
for method in ('__member_new__', '__new__'):
for possible in (member_type, first_enum):
try:
target = possible.__dict__[method]
except (AttributeError, KeyError):
target = getattr(possible, method, None)
if target not in [
None,
N__new__,
O__new__,
E__new__,
]:
if method == '__member_new__':
classdict['__new__'] = target
return None, False, True
if isinstance(target, staticmethod):
target = target.__get__(member_type)
__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__, False, use_args
else:
@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 __member_new__
__new__ = classdict.get('__new__', None)
# should __new__ be saved as __member_new__ later?
save_new = __new__ is not None
if __new__ is None:
# check all possibles for __member_new__ before falling back to
# __new__
for method in ('__member_new__', '__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
########################################################
# In order to support Python 2 and 3 with a single
# codebase we have to create the Enum methods separately
# and then use the `type(name, bases, dict)` method to
# create the class.
########################################################
temp_enum_dict = {}
temp_enum_dict['__doc__'] = "Generic enumeration.\n\n Derive from this class to define new enumerations.\n\n"
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)
value = value.value
#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__))
temp_enum_dict['__new__'] = __new__
del __new__
def __repr__(self):
return "<%s.%s: %r>" % (
self.__class__.__name__, self._name_, self._value_)
temp_enum_dict['__repr__'] = __repr__
del __repr__
def __str__(self):
return "%s.%s" % (self.__class__.__name__, self._name_)
temp_enum_dict['__str__'] = __str__
del __str__
def __dir__(self):
added_behavior = [
m
for cls in self.__class__.mro()
for m in cls.__dict__
if m[0] != '_'
]
return (['__class__', '__doc__', '__module__', ] + added_behavior)
temp_enum_dict['__dir__'] = __dir__
del __dir__
def __format__(self, format_spec):
# mixed-in Enums should use the mixed-in type's __format__, otherwise
# we can get strange results with the Enum name showing up instead of
# the value
# pure Enum branch
if self._member_type_ is object:
cls = str
val = str(self)
# mix-in branch
else:
cls = self._member_type_
val = self.value
return cls.__format__(val, format_spec)
temp_enum_dict['__format__'] = __format__
del __format__
####################################
# Python's less than 2.6 use __cmp__
if pyver < 2.6:
def __cmp__(self, other):
if type(other) is self.__class__:
if self is other:
return 0
return -1
return NotImplemented
raise TypeError("unorderable types: %s() and %s()" % (self.__class__.__name__, other.__class__.__name__))
temp_enum_dict['__cmp__'] = __cmp__
del __cmp__
else:
def __le__(self, other):
raise TypeError("unorderable types: %s() <= %s()" % (self.__class__.__name__, other.__class__.__name__))
temp_enum_dict['__le__'] = __le__
del __le__
def __lt__(self, other):
raise TypeError("unorderable types: %s() < %s()" % (self.__class__.__name__, other.__class__.__name__))
temp_enum_dict['__lt__'] = __lt__
del __lt__
def __ge__(self, other):
raise TypeError("unorderable types: %s() >= %s()" % (self.__class__.__name__, other.__class__.__name__))
temp_enum_dict['__ge__'] = __ge__
del __ge__
def __gt__(self, other):
raise TypeError("unorderable types: %s() > %s()" % (self.__class__.__name__, other.__class__.__name__))
temp_enum_dict['__gt__'] = __gt__
del __gt__
def __eq__(self, other):
if type(other) is self.__class__:
return self is other
return NotImplemented
temp_enum_dict['__eq__'] = __eq__
del __eq__
def __ne__(self, other):
if type(other) is self.__class__:
return self is not other
return NotImplemented
temp_enum_dict['__ne__'] = __ne__
del __ne__
def __hash__(self):
return hash(self._name_)
temp_enum_dict['__hash__'] = __hash__
del __hash__
def __reduce_ex__(self, proto):
return self.__class__, (self._value_, )
temp_enum_dict['__reduce_ex__'] = __reduce_ex__
del __reduce_ex__
# _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_
temp_enum_dict['name'] = name
del name
@_RouteClassAttributeToGetattr
def value(self):
return self._value_
temp_enum_dict['value'] = value
del value
Enum = EnumMeta('Enum', (object, ), temp_enum_dict)
del temp_enum_dict
# Enum has now been created
###########################
class IntEnum(int, Enum):
"""Enum where members are also (and must be) ints"""
def unique(enumeration):
"""Class decorator that ensures only unique members exist in an enumeration."""
duplicates = []
for name, member in enumeration.__members__.items():
if name != member.name:
duplicates.append((name, member.name))
if duplicates:
duplicate_names = ', '.join(
["%s -> %s" % (alias, name) for (alias, name) in duplicates]
)
raise ValueError('duplicate names found in %r: %s' %
(enumeration, duplicate_names)
)
return enumeration
Keith Burns (alagalah)
Ed Warnicke