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Copyright (c) 2013, Ethan Furman.
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
Redistributions of source code must retain the above
copyright notice, this list of conditions and the
following disclaimer.
Redistributions in binary form must reproduce the above
copyright notice, this list of conditions and the following
disclaimer in the documentation and/or other materials
provided with the distribution.
Neither the name Ethan Furman nor the names of any
contributors may be used to endorse or promote products
derived from this software without specific prior written
permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.

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enum34 is the new Python stdlib enum module available in Python 3.4
backported for previous versions of Python from 2.4 to 3.3.

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"""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

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``enum`` --- support for enumerations
========================================
.. :synopsis: enumerations are sets of symbolic names bound to unique, constant
values.
.. :moduleauthor:: Ethan Furman <ethan@stoneleaf.us>
.. :sectionauthor:: Barry Warsaw <barry@python.org>,
.. :sectionauthor:: Eli Bendersky <eliben@gmail.com>,
.. :sectionauthor:: Ethan Furman <ethan@stoneleaf.us>
----------------
An enumeration is a set of symbolic names (members) bound to unique, constant
values. Within an enumeration, the members can be compared by identity, and
the enumeration itself can be iterated over.
Module Contents
---------------
This module defines two enumeration classes that can be used to define unique
sets of names and values: ``Enum`` and ``IntEnum``. It also defines
one decorator, ``unique``.
``Enum``
Base class for creating enumerated constants. See section `Functional API`_
for an alternate construction syntax.
``IntEnum``
Base class for creating enumerated constants that are also subclasses of ``int``.
``unique``
Enum class decorator that ensures only one name is bound to any one value.
Creating an Enum
----------------
Enumerations are created using the ``class`` syntax, which makes them
easy to read and write. An alternative creation method is described in
`Functional API`_. To define an enumeration, subclass ``Enum`` as
follows::
>>> from enum import Enum
>>> class Color(Enum):
... red = 1
... green = 2
... blue = 3
Note: Nomenclature
- The class ``Color`` is an *enumeration* (or *enum*)
- The attributes ``Color.red``, ``Color.green``, etc., are
*enumeration members* (or *enum members*).
- The enum members have *names* and *values* (the name of
``Color.red`` is ``red``, the value of ``Color.blue`` is
``3``, etc.)
Note:
Even though we use the ``class`` syntax to create Enums, Enums
are not normal Python classes. See `How are Enums different?`_ for
more details.
Enumeration members have human readable string representations::
>>> print(Color.red)
Color.red
...while their ``repr`` has more information::
>>> print(repr(Color.red))
<Color.red: 1>
The *type* of an enumeration member is the enumeration it belongs to::
>>> type(Color.red)
<enum 'Color'>
>>> isinstance(Color.green, Color)
True
>>>
Enum members also have a property that contains just their item name::
>>> print(Color.red.name)
red
Enumerations support iteration. In Python 3.x definition order is used; in
Python 2.x the definition order is not available, but class attribute
``__order__`` is supported; otherwise, value order is used::
>>> class Shake(Enum):
... __order__ = 'vanilla chocolate cookies mint' # only needed in 2.x
... vanilla = 7
... chocolate = 4
... cookies = 9
... mint = 3
...
>>> for shake in Shake:
... print(shake)
...
Shake.vanilla
Shake.chocolate
Shake.cookies
Shake.mint
The ``__order__`` attribute is always removed, and in 3.x it is also ignored
(order is definition order); however, in the stdlib version it will be ignored
but not removed.
Enumeration members are hashable, so they can be used in dictionaries and sets::
>>> apples = {}
>>> apples[Color.red] = 'red delicious'
>>> apples[Color.green] = 'granny smith'
>>> apples == {Color.red: 'red delicious', Color.green: 'granny smith'}
True
Programmatic access to enumeration members and their attributes
---------------------------------------------------------------
Sometimes it's useful to access members in enumerations programmatically (i.e.
situations where ``Color.red`` won't do because the exact color is not known
at program-writing time). ``Enum`` allows such access::
>>> Color(1)
<Color.red: 1>
>>> Color(3)
<Color.blue: 3>
If you want to access enum members by *name*, use item access::
>>> Color['red']
<Color.red: 1>
>>> Color['green']
<Color.green: 2>
If have an enum member and need its ``name`` or ``value``::
>>> member = Color.red
>>> member.name
'red'
>>> member.value
1
Duplicating enum members and values
-----------------------------------
Having two enum members (or any other attribute) with the same name is invalid;
in Python 3.x this would raise an error, but in Python 2.x the second member
simply overwrites the first::
>>> # python 2.x
>>> class Shape(Enum):
... square = 2
... square = 3
...
>>> Shape.square
<Shape.square: 3>
>>> # python 3.x
>>> class Shape(Enum):
... square = 2
... square = 3
Traceback (most recent call last):
...
TypeError: Attempted to reuse key: 'square'
However, two enum members are allowed to have the same value. Given two members
A and B with the same value (and A defined first), B is an alias to A. By-value
lookup of the value of A and B will return A. By-name lookup of B will also
return A::
>>> class Shape(Enum):
... __order__ = 'square diamond circle alias_for_square' # only needed in 2.x
... square = 2
... diamond = 1
... circle = 3
... alias_for_square = 2
...
>>> Shape.square
<Shape.square: 2>
>>> Shape.alias_for_square
<Shape.square: 2>
>>> Shape(2)
<Shape.square: 2>
Allowing aliases is not always desirable. ``unique`` can be used to ensure
that none exist in a particular enumeration::
>>> from enum import unique
>>> @unique
... class Mistake(Enum):
... __order__ = 'one two three four' # only needed in 2.x
... one = 1
... two = 2
... three = 3
... four = 3
Traceback (most recent call last):
...
ValueError: duplicate names found in <enum 'Mistake'>: four -> three
Iterating over the members of an enum does not provide the aliases::
>>> list(Shape)
[<Shape.square: 2>, <Shape.diamond: 1>, <Shape.circle: 3>]
The special attribute ``__members__`` is a dictionary mapping names to members.
It includes all names defined in the enumeration, including the aliases::
>>> for name, member in sorted(Shape.__members__.items()):
... name, member
...
('alias_for_square', <Shape.square: 2>)
('circle', <Shape.circle: 3>)
('diamond', <Shape.diamond: 1>)
('square', <Shape.square: 2>)
The ``__members__`` attribute can be used for detailed programmatic access to
the enumeration members. For example, finding all the aliases::
>>> [name for name, member in Shape.__members__.items() if member.name != name]
['alias_for_square']
Comparisons
-----------
Enumeration members are compared by identity::
>>> Color.red is Color.red
True
>>> Color.red is Color.blue
False
>>> Color.red is not Color.blue
True
Ordered comparisons between enumeration values are *not* supported. Enum
members are not integers (but see `IntEnum`_ below)::
>>> Color.red < Color.blue
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unorderable types: Color() < Color()
.. warning::
In Python 2 *everything* is ordered, even though the ordering may not
make sense. If you want your enumerations to have a sensible ordering
check out the `OrderedEnum`_ recipe below.
Equality comparisons are defined though::
>>> Color.blue == Color.red
False
>>> Color.blue != Color.red
True
>>> Color.blue == Color.blue
True
Comparisons against non-enumeration values will always compare not equal
(again, ``IntEnum`` was explicitly designed to behave differently, see
below)::
>>> Color.blue == 2
False
Allowed members and attributes of enumerations
----------------------------------------------
The examples above use integers for enumeration values. Using integers is
short and handy (and provided by default by the `Functional API`_), but not
strictly enforced. In the vast majority of use-cases, one doesn't care what
the actual value of an enumeration is. But if the value *is* important,
enumerations can have arbitrary values.
Enumerations are Python classes, and can have methods and special methods as
usual. If we have this enumeration::
>>> class Mood(Enum):
... funky = 1
... happy = 3
...
... def describe(self):
... # self is the member here
... return self.name, self.value
...
... def __str__(self):
... return 'my custom str! {0}'.format(self.value)
...
... @classmethod
... def favorite_mood(cls):
... # cls here is the enumeration
... return cls.happy
Then::
>>> Mood.favorite_mood()
<Mood.happy: 3>
>>> Mood.happy.describe()
('happy', 3)
>>> str(Mood.funky)
'my custom str! 1'
The rules for what is allowed are as follows: _sunder_ names (starting and
ending with a single underscore) are reserved by enum and cannot be used;
all other attributes defined within an enumeration will become members of this
enumeration, with the exception of *__dunder__* names and descriptors (methods
are also descriptors).
Note:
If your enumeration defines ``__new__`` and/or ``__init__`` then
whatever value(s) were given to the enum member will be passed into
those methods. See `Planet`_ for an example.
Restricted subclassing of enumerations
--------------------------------------
Subclassing an enumeration is allowed only if the enumeration does not define
any members. So this is forbidden::
>>> class MoreColor(Color):
... pink = 17
Traceback (most recent call last):
...
TypeError: Cannot extend enumerations
But this is allowed::
>>> class Foo(Enum):
... def some_behavior(self):
... pass
...
>>> class Bar(Foo):
... happy = 1
... sad = 2
...
Allowing subclassing of enums that define members would lead to a violation of
some important invariants of types and instances. On the other hand, it makes
sense to allow sharing some common behavior between a group of enumerations.
(See `OrderedEnum`_ for an example.)
Pickling
--------
Enumerations can be pickled and unpickled::
>>> from enum.test_enum import Fruit
>>> from pickle import dumps, loads
>>> Fruit.tomato is loads(dumps(Fruit.tomato, 2))
True
The usual restrictions for pickling apply: picklable enums must be defined in
the top level of a module, since unpickling requires them to be importable
from that module.
Note:
With pickle protocol version 4 (introduced in Python 3.4) it is possible
to easily pickle enums nested in other classes.
Functional API
--------------
The ``Enum`` class is callable, providing the following functional API::
>>> Animal = Enum('Animal', 'ant bee cat dog')
>>> Animal
<enum 'Animal'>
>>> Animal.ant
<Animal.ant: 1>
>>> Animal.ant.value
1
>>> list(Animal)
[<Animal.ant: 1>, <Animal.bee: 2>, <Animal.cat: 3>, <Animal.dog: 4>]
The semantics of this API resemble ``namedtuple``. The first argument
of the call to ``Enum`` is the name of the enumeration.
The second argument is the *source* of enumeration member names. It can be a
whitespace-separated string of names, a sequence of names, a sequence of
2-tuples with key/value pairs, or a mapping (e.g. dictionary) of names to
values. The last two options enable assigning arbitrary values to
enumerations; the others auto-assign increasing integers starting with 1. A
new class derived from ``Enum`` is returned. In other words, the above
assignment to ``Animal`` is equivalent to::
>>> class Animals(Enum):
... ant = 1
... bee = 2
... cat = 3
... dog = 4
Pickling enums created with the functional API can be tricky as frame stack
implementation details are used to try and figure out which module the
enumeration is being created in (e.g. it will fail if you use a utility
function in separate module, and also may not work on IronPython or Jython).
The solution is to specify the module name explicitly as follows::
>>> Animals = Enum('Animals', 'ant bee cat dog', module=__name__)
Derived Enumerations
--------------------
IntEnum
^^^^^^^
A variation of ``Enum`` is provided which is also a subclass of
``int``. Members of an ``IntEnum`` can be compared to integers;
by extension, integer enumerations of different types can also be compared
to each other::
>>> from enum import IntEnum
>>> class Shape(IntEnum):
... circle = 1
... square = 2
...
>>> class Request(IntEnum):
... post = 1
... get = 2
...
>>> Shape == 1
False
>>> Shape.circle == 1
True
>>> Shape.circle == Request.post
True
However, they still can't be compared to standard ``Enum`` enumerations::
>>> class Shape(IntEnum):
... circle = 1
... square = 2
...
>>> class Color(Enum):
... red = 1
... green = 2
...
>>> Shape.circle == Color.red
False
``IntEnum`` values behave like integers in other ways you'd expect::
>>> int(Shape.circle)
1
>>> ['a', 'b', 'c'][Shape.circle]
'b'
>>> [i for i in range(Shape.square)]
[0, 1]
For the vast majority of code, ``Enum`` is strongly recommended,
since ``IntEnum`` breaks some semantic promises of an enumeration (by
being comparable to integers, and thus by transitivity to other
unrelated enumerations). It should be used only in special cases where
there's no other choice; for example, when integer constants are
replaced with enumerations and backwards compatibility is required with code
that still expects integers.
Others
^^^^^^
While ``IntEnum`` is part of the ``enum`` module, it would be very
simple to implement independently::
class IntEnum(int, Enum):
pass
This demonstrates how similar derived enumerations can be defined; for example
a ``StrEnum`` that mixes in ``str`` instead of ``int``.
Some rules:
1. When subclassing ``Enum``, mix-in types must appear before
``Enum`` itself in the sequence of bases, as in the ``IntEnum``
example above.
2. While ``Enum`` can have members of any type, once you mix in an
additional type, all the members must have values of that type, e.g.
``int`` above. This restriction does not apply to mix-ins which only
add methods and don't specify another data type such as ``int`` or
``str``.
3. When another data type is mixed in, the ``value`` attribute is *not the
same* as the enum member itself, although it is equivalant and will compare
equal.
4. %-style formatting: ``%s`` and ``%r`` call ``Enum``'s ``__str__`` and
``__repr__`` respectively; other codes (such as ``%i`` or ``%h`` for
IntEnum) treat the enum member as its mixed-in type.
Note: Prior to Python 3.4 there is a bug in ``str``'s %-formatting: ``int``
subclasses are printed as strings and not numbers when the ``%d``, ``%i``,
or ``%u`` codes are used.
5. ``str.__format__`` (or ``format``) will use the mixed-in
type's ``__format__``. If the ``Enum``'s ``str`` or
``repr`` is desired use the ``!s`` or ``!r`` ``str`` format codes.
Decorators
----------
unique
^^^^^^
A ``class`` decorator specifically for enumerations. It searches an
enumeration's ``__members__`` gathering any aliases it finds; if any are
found ``ValueError`` is raised with the details::
>>> @unique
... class NoDupes(Enum):
... first = 'one'
... second = 'two'
... third = 'two'
Traceback (most recent call last):
...
ValueError: duplicate names found in <enum 'NoDupes'>: third -> second
Interesting examples
--------------------
While ``Enum`` and ``IntEnum`` are expected to cover the majority of
use-cases, they cannot cover them all. Here are recipes for some different
types of enumerations that can be used directly, or as examples for creating
one's own.
AutoNumber
^^^^^^^^^^
Avoids having to specify the value for each enumeration member::
>>> class AutoNumber(Enum):
... def __new__(cls):
... value = len(cls.__members__) + 1
... obj = object.__new__(cls)
... obj._value_ = value
... return obj
...
>>> class Color(AutoNumber):
... __order__ = "red green blue" # only needed in 2.x
... red = ()
... green = ()
... blue = ()
...
>>> Color.green.value == 2
True
Note:
The `__new__` method, if defined, is used during creation of the Enum
members; it is then replaced by Enum's `__new__` which is used after
class creation for lookup of existing members. Due to the way Enums are
supposed to behave, there is no way to customize Enum's `__new__`.
UniqueEnum
^^^^^^^^^^
Raises an error if a duplicate member name is found instead of creating an
alias::
>>> class UniqueEnum(Enum):
... def __init__(self, *args):
... cls = self.__class__
... if any(self.value == e.value for e in cls):
... a = self.name
... e = cls(self.value).name
... raise ValueError(
... "aliases not allowed in UniqueEnum: %r --> %r"
... % (a, e))
...
>>> class Color(UniqueEnum):
... red = 1
... green = 2
... blue = 3
... grene = 2
Traceback (most recent call last):
...
ValueError: aliases not allowed in UniqueEnum: 'grene' --> 'green'
OrderedEnum
^^^^^^^^^^^
An ordered enumeration that is not based on ``IntEnum`` and so maintains
the normal ``Enum`` invariants (such as not being comparable to other
enumerations)::
>>> class OrderedEnum(Enum):
... def __ge__(self, other):
... if self.__class__ is other.__class__:
... return self._value_ >= other._value_
... return NotImplemented
... def __gt__(self, other):
... if self.__class__ is other.__class__:
... return self._value_ > other._value_
... return NotImplemented
... def __le__(self, other):
... if self.__class__ is other.__class__:
... return self._value_ <= other._value_
... return NotImplemented
... def __lt__(self, other):
... if self.__class__ is other.__class__:
... return self._value_ < other._value_
... return NotImplemented
...
>>> class Grade(OrderedEnum):
... __ordered__ = 'A B C D F'
... A = 5
... B = 4
... C = 3
... D = 2
... F = 1
...
>>> Grade.C < Grade.A
True
Planet
^^^^^^
If ``__new__`` or ``__init__`` is defined the value of the enum member
will be passed to those methods::
>>> class Planet(Enum):
... MERCURY = (3.303e+23, 2.4397e6)
... VENUS = (4.869e+24, 6.0518e6)
... EARTH = (5.976e+24, 6.37814e6)
... MARS = (6.421e+23, 3.3972e6)
... JUPITER = (1.9e+27, 7.1492e7)
... SATURN = (5.688e+26, 6.0268e7)
... URANUS = (8.686e+25, 2.5559e7)
... NEPTUNE = (1.024e+26, 2.4746e7)
... def __init__(self, mass, radius):
... self.mass = mass # in kilograms
... self.radius = radius # in meters
... @property
... def surface_gravity(self):
... # universal gravitational constant (m3 kg-1 s-2)
... G = 6.67300E-11
... return G * self.mass / (self.radius * self.radius)
...
>>> Planet.EARTH.value
(5.976e+24, 6378140.0)
>>> Planet.EARTH.surface_gravity
9.802652743337129
How are Enums different?
------------------------
Enums have a custom metaclass that affects many aspects of both derived Enum
classes and their instances (members).
Enum Classes
^^^^^^^^^^^^
The ``EnumMeta`` metaclass is responsible for providing the
``__contains__``, ``__dir__``, ``__iter__`` and other methods that
allow one to do things with an ``Enum`` class that fail on a typical
class, such as ``list(Color)`` or ``some_var in Color``. ``EnumMeta`` is
responsible for ensuring that various other methods on the final ``Enum``
class are correct (such as ``__new__``, ``__getnewargs__``,
``__str__`` and ``__repr__``)
Enum Members (aka instances)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The most interesting thing about Enum members is that they are singletons.
``EnumMeta`` creates them all while it is creating the ``Enum``
class itself, and then puts a custom ``__new__`` in place to ensure
that no new ones are ever instantiated by returning only the existing
member instances.
Finer Points
^^^^^^^^^^^^
Enum members are instances of an Enum class, and even though they are
accessible as ``EnumClass.member``, they are not accessible directly from
the member::
>>> Color.red
<Color.red: 1>
>>> Color.red.blue
Traceback (most recent call last):
...
AttributeError: 'Color' object has no attribute 'blue'
Likewise, ``__members__`` is only available on the class.
In Python 3.x ``__members__`` is always an ``OrderedDict``, with the order being
the definition order. In Python 2.7 ``__members__`` is an ``OrderedDict`` if
``__order__`` was specified, and a plain ``dict`` otherwise. In all other Python
2.x versions ``__members__`` is a plain ``dict`` even if ``__order__`` was specified
as the ``OrderedDict`` type didn't exist yet.
If you give your ``Enum`` subclass extra methods, like the `Planet`_
class above, those methods will show up in a `dir` of the member,
but not of the class::
>>> dir(Planet)
['EARTH', 'JUPITER', 'MARS', 'MERCURY', 'NEPTUNE', 'SATURN', 'URANUS',
'VENUS', '__class__', '__doc__', '__members__', '__module__']
>>> dir(Planet.EARTH)
['__class__', '__doc__', '__module__', 'name', 'surface_gravity', 'value']
A ``__new__`` method will only be used for the creation of the
``Enum`` members -- after that it is replaced. This means if you wish to
change how ``Enum`` members are looked up you either have to write a
helper function or a ``classmethod``.

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"""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

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