Python: aenum enumeration generates error

Question

Today I tried an enumeration with aenum (like in this answer: https://stackoverflow.com/a/1695250/4720441):

orientation = Enum('red', 'yellow', 'green', 'orange')

but this generated an error in the aenum library:

File "C:\Python\27\lib\site-packages\aenum__init__.py", line 1417, in _get_mixins_ issubclass(base, Enum) and TypeError: issubclass() arg 1 must be a class

How can I fix this?

Answer 1

The various ways to create an Enum using call syntax are:

# starts at 1
SomeEnum = Enum('SomeEnum', 'member1 member2 member3')

# starts at 1
SomeEnum = Enum('SomeEnum', ['member1', 'member2', 'member3'])

# values manually assigned
SomeEnum = Enum('SomeEnum', [('member1', 3), ('member2', 4), ('member3', 5)])

# values manually assigned
SomeEnum = Enum('SomeEnum', {'member1': 6, 'member2': 7, 'member3': 8})

# starts at 9
SomeEnum = Enum('SomeEnum', 'member1 member2 member3', start=9)

This is the same across the stdlib version, enum34, and aenum¹. The enum² package is an old-style library.

---

The stdlib versions contain:

3.4

• Enum
• IntEnum
• unique

3.6

• Flag
• IntFlag

*enum34 is the same as the 3.4 stdlib.

aenum

contains the above, plus:

• OrderedEnum - members can be compared against each other
• AutoNumberEnum - value is automatically generated
• MultiValueEnum - members can be looked up with have multiple values
• NoAliasEnum - duplicates are unique, not aliases

and various helpers to manipulate the construction of enumerations:

• skip - prevents attributes from becoming enum members (attribute stays the same)
• constant -- to prevent attributes from becoming enum members (attribute becomes a type of read-only property)
• extend_enum - add new members to an existing enumeration (useful when the Enum is built in stages)

And extra related types:

• NamedConstant - No enumeration fanciness, just a value with a name
• NamedTuple - similar to the stdlib namedtuple, but built using metaclasses instead of eval

---

¹ Disclosure: I am the primary author of the Python stdlib Enum, the enum34 backport, and the Advanced Enumeration (aenum) library.

² The author of the older enum library also helped with the stdlib version.

Answer 2

aenum.Enum is not constructed like this (see https://bitbucket.org/stoneleaf/aenum).

Instead you should be passing in a first argument containing the Enum name, and a second argument corresponding to a space separated list of enum keys you want enumerated.

E.g.

orientation = Enum('red', 'yellow green orange')

Note on the answer at https://stackoverflow.com/a/1695250/4720441

In this answer, the poster creates an enum function, which combines it's arguments into a dict, and then passes that dict to the standard Enum constructor (as the third argument).