# Enum枚举类
# 枚举的使用
from enum import Enum
# 这种情况下是从1开始自动赋予
Month = Enum('Month', ('Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'))
for name, member in Month.__members__.items():
print(name, '=>', member, ',', member.value)
# Jan => Month.Jan , 1
# Feb => Month.Feb , 2
# Mar => Month.Mar , 3
# Apr => Month.Apr , 4
# May => Month.May , 5
# Jun => Month.Jun , 6
# Jul => Month.Jul , 7
# Aug => Month.Aug , 8
# Sep => Month.Sep , 9
# Oct => Month.Oct , 10
# Nov => Month.Nov , 11
# Dec => Month.Dec , 12
# 枚举类
特点：
保证不可在类内修改，不可实例化
枚举中标签名唯一
使用unique装饰器确保值唯一
默认情况下键不唯一后定义的视为别名，会被认为是同一个枚举类型，迭代时不可见但可从__members__中得到
class Weekday(Enum): Sun = 0 # Sun的value被设定为0 Mon = 1 Tue = 2 Wed = 3 Thu = 4 Fri = 5 Sat = 6 SUN_AGAIN = 0 for member in Weekday: print(member) # Weekday.Sun # Weekday.Mon # Weekday.Tue # Weekday.Wed # Weekday.Thu # Weekday.Fri # Weekday.Sat for name,member in Weekday.__members__.items(): print(name, '=>', member) # Sun => Weekday.Sun # Mon => Weekday.Mon # Tue => Weekday.Tue # Wed => Weekday.Wed # Thu => Weekday.Thu # Fri => Weekday.Fri # Sat => Weekday.Sat # SUN_AGAIN => Weekday.Sun
可以以类似字典的形式从标签名获得标签值，也可以从标签值去获得标签名
from enum import Enum, unique
@unique
class Weekday(Enum):
Sun = 0 # Sun的value被设定为0
Mon = 1
Tue = 2
Wed = 3
Thu = 4
Fri = 5
Sat = 6
print(Weekday.Mon) # Weekday.Mon
print(Weekday.Mon.name) # Mon
print(Weekday.Mon.value) # 1
print(type(Weekday)) # <class 'enum.EnumMeta'>
print(type(Weekday.Mon)) # <enum 'Weekday'>
print(type(Weekday.Mon.name)) # <class 'str'>
print(type(Weekday.Mon.value)) # <class 'int'>
print(Weekday["Mon"]) # Weekday.Mon
print(Weekday["Mon"] == Weekday.Mon) # True
print(Weekday(1)) # Weekday.Mon
for member in Weekday:
print(member)
# Weekday.Sun
# Weekday.Mon
# Weekday.Tue
# Weekday.Wed
# Weekday.Thu
# Weekday.Fri
# Weekday.Sat
for name,member in Weekday.__members__.items():
print(name, '=>', member)
# Sun => Weekday.Sun
# Mon => Weekday.Mon
# Tue => Weekday.Tue
# Wed => Weekday.Wed
# Thu => Weekday.Thu
# Fri => Weekday.Fri
# Sat => Weekday.Sat
from enum import Enum
class CommonExceptionMessage(Enum):
UNKNOWN_SERVER_EXCEPTION = ["服务器未知内部错误", 500]
@property
def code(self):
return self.value[1]
@property
def messgae(self):
return self.value[0]
print(CommonExceptionMessage.UNKNOWN_SERVER_EXCEPTION.code)
print(CommonExceptionMessage.UNKNOWN_SERVER_EXCEPTION.messgae)
print(CommonExceptionMessage.UNKNOWN_SERVER_EXCEPTION.value)
# Enum实现
class EnumMeta(type):
"""Metaclass for Enum"""
@classmethod
def __prepare__(metacls, cls, bases):
# create the namespace dict
enum_dict = _EnumDict()
# inherit previous flags and _generate_next_value_ function
member_type, first_enum = metacls._get_mixins_(bases)
if first_enum is not None:
enum_dict['_generate_next_value_'] = getattr(first_enum, '_generate_next_value_', None)
return enum_dict
def __new__(metacls, cls, bases, classdict):
# 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).
#
# remove any keys listed in _ignore_
classdict.setdefault('_ignore_', []).append('_ignore_')
ignore = classdict['_ignore_']
for key in ignore:
classdict.pop(key, None)
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
enum_members = {k: classdict[k] for k in classdict._member_names}
for name in classdict._member_names:
del classdict[name]
# adjust the sunders
_order_ = classdict.pop('_order_', None)
# check for illegal enum names (any others?)
invalid_names = set(enum_members) & {'mro', ''}
if invalid_names:
raise ValueError('Invalid enum member name: {0}'.format(
','.join(invalid_names)))
# create a default docstring if one has not been provided
if '__doc__' not in classdict:
classdict['__doc__'] = 'An enumeration.'
# 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
# save DynamicClassAttribute attributes from super classes so we know
# if we can take the shortcut of storing members in the class dict
dynamic_attributes = {k for c in enum_class.mro()
for k, v in c.__dict__.items()
if isinstance(v, DynamicClassAttribute)}
# Reverse value->name map for hashable values.
enum_class._value2member_map_ = {}
# 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.
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)
# 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 = enum_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_'):
if member_type is object:
enum_member._value_ = value
else:
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)
# performance boost for any member that would not shadow
# a DynamicClassAttribute
if member_name not in dynamic_attributes:
setattr(enum_class, member_name, enum_member)
# now add to _member_map_
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__', '__format__', '__reduce_ex__'):
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__
# py3 support for definition order (helps keep py2/py3 code in sync)
if _order_ is not None:
if isinstance(_order_, str):
_order_ = _order_.replace(',', ' ').split()
if _order_ != enum_class._member_names_:
raise TypeError('member order does not match _order_')
return enum_class
def __bool__(self):
"""
classes/types should always be True.
"""
return True
def __call__(cls, value, names=None, *, module=None, qualname=None, type=None, start=1):
"""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:
`value` will be the name of the new class.
`names` should be either a string of white-space/comma delimited names
(values will start at `start`), or an iterator/mapping of name, value pairs.
`module` should be set to the module this class is being created in;
if it is not set, an attempt to find that module will be made, but if
it fails the class will not be picklable.
`qualname` should be set to the actual location this class can be found
at in its module; by default it is set to the global scope. If this is
not correct, unpickling will fail in some circumstances.
`type`, if set, will be mixed in as the first base class.
"""
if 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, qualname=qualname, type=type, start=start)
def __contains__(cls, member):
if not isinstance(member, Enum):
import warnings
warnings.warn(
"using non-Enums in containment checks will raise "
"TypeError in Python 3.8",
DeprecationWarning, 2)
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().__delattr__(attr)
def __dir__(self):
return (['__class__', '__doc__', '__members__', '__module__'] +
self._member_names_)
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_)
@property
def __members__(cls):
"""Returns a mapping of member name->value.
This mapping lists all enum members, including aliases. Note that this
is a read-only view of the internal mapping.
"""
return MappingProxyType(cls._member_map_)
def __repr__(cls):
return "<enum %r>" % cls.__name__
def __reversed__(cls):
return (cls._member_map_[name] for name in reversed(cls._member_names_))
def __setattr__(cls, name, value):
"""Block attempts to reassign Enum members.
A simple assignment to the class namespace only changes one of the
several possible ways to get an Enum member from the Enum class,
resulting in an inconsistent Enumeration.
"""
member_map = cls.__dict__.get('_member_map_', {})
if name in member_map:
raise AttributeError('Cannot reassign members.')
super().__setattr__(name, value)
def _create_(cls, class_name, names, *, module=None, qualname=None, type=None, start=1):
"""Convenience method to create a new Enum class.
`names` can be:
* A string containing member names, separated either with spaces or
commas. Values are incremented by 1 from `start`.
* An iterable of member names. Values are incremented by 1 from `start`.
* An iterable of (member name, value) pairs.
* A mapping of member name -> value pairs.
"""
metacls = cls.__class__
bases = (cls, ) if type is None else (type, cls)
_, first_enum = cls._get_mixins_(bases)
classdict = metacls.__prepare__(class_name, bases)
# special processing needed for names?
if isinstance(names, str):
names = names.replace(',', ' ').split()
if isinstance(names, (tuple, list)) and names and isinstance(names[0], str):
original_names, names = names, []
last_values = []
for count, name in enumerate(original_names):
value = first_enum._generate_next_value_(name, start, count, last_values[:])
last_values.append(value)
names.append((name, value))
# 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, KeyError) as exc:
pass
if module is None:
_make_class_unpicklable(enum_class)
else:
enum_class.__module__ = module
if qualname is not None:
enum_class.__qualname__ = qualname
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
def _find_data_type(bases):
for chain in bases:
for base in chain.__mro__:
if base is object:
continue
elif '__new__' in base.__dict__:
if issubclass(base, Enum):
continue
return base
# ensure final parent class is an Enum derivative, find any concrete
# data type, and check that Enum has no members
first_enum = bases[-1]
if not issubclass(first_enum, Enum):
raise TypeError("new enumerations should be created as "
"`EnumName([mixin_type, ...] [data_type,] enum_type)`")
member_type = _find_data_type(bases) or object
if first_enum._member_names_:
raise TypeError("Cannot extend enumerations")
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:
return cls._value2member_map_[value]
except KeyError:
# Not found, no need to do long O(n) search
pass
except TypeError:
# not there, now do long search -- O(n) behavior
for member in cls._member_map_.values():
if member._value_ == value:
return member
# still not found -- try _missing_ hook
try:
exc = None
result = cls._missing_(value)
except Exception as e:
exc = e
result = None
if isinstance(result, cls):
return result
else:
ve_exc = ValueError("%r is not a valid %s" % (value, cls.__name__))
if result is None and exc is None:
raise ve_exc
elif exc is None:
exc = TypeError(
'error in %s._missing_: returned %r instead of None or a valid member'
% (cls.__name__, result)
)
exc.__context__ = ve_exc
raise exc
def _generate_next_value_(name, start, count, last_values):
for last_value in reversed(last_values):
try:
return last_value + 1
except TypeError:
pass
else:
return start
@classmethod
def _missing_(cls, value):
raise ValueError("%r 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):
added_behavior = [
m
for cls in self.__class__.mro()
for m in cls.__dict__
if m[0] != '_' and m not in self._member_map_
]
return (['__class__', '__doc__', '__module__'] + added_behavior)
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)
def __hash__(self):
return hash(self._name_)
def __reduce_ex__(self, proto):
return self.__class__, (self._value_, )
# DynamicClassAttribute 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.
@DynamicClassAttribute
def name(self):
"""The name of the Enum member."""
return self._name_
@DynamicClassAttribute
def value(self):
"""The value of the Enum member."""
return self._value_
@classmethod
def _convert(cls, name, module, filter, source=None):
"""
Create a new Enum subclass that replaces a collection of global constants
"""
# convert all constants from source (or module) that pass filter() to
# a new Enum called name, and export the enum and its members back to
# module;
# also, replace the __reduce_ex__ method so unpickling works in
# previous Python versions
module_globals = vars(sys.modules[module])
if source:
source = vars(source)
else:
source = module_globals
# We use an OrderedDict of sorted source keys so that the
# _value2member_map is populated in the same order every time
# for a consistent reverse mapping of number to name when there
# are multiple names for the same number rather than varying
# between runs due to hash randomization of the module dictionary.
members = [
(name, source[name])
for name in source.keys()
if filter(name)]
try:
# sort by value
members.sort(key=lambda t: (t[1], t[0]))
except TypeError:
# unless some values aren't comparable, in which case sort by name
members.sort(key=lambda t: t[0])
cls = cls(name, members, module=module)
cls.__reduce_ex__ = _reduce_ex_by_name
module_globals.update(cls.__members__)
module_globals[name] = cls
return cls
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