Enums don't support nested classes

[edwardcwang]

BPO	33976
Nosy	@warsaw, @ethanfurman, @edwardcwang
PRs	bpo-33976: support nested classes in Enum #7950

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/ethanfurman'
closed_at = None
created_at = <Date 2018-06-27.04:00:50.213>
labels = ['type-bug']
title = "Enums don't support nested classes"
updated_at = <Date 2019-07-17.17:25:12.823>
user = 'https://github.com/edwardcwang'

bugs.python.org fields:

activity = <Date 2019-07-17.17:25:12.823>
actor = 'ethan.furman'
assignee = 'ethan.furman'
closed = False
closed_date = None
closer = None
components = []
creation = <Date 2018-06-27.04:00:50.213>
creator = 'edwardw'
dependencies = []
files = []
hgrepos = []
issue_num = 33976
keywords = ['patch']
message_count = 4.0
messages = ['320541', '320548', '320550', '348073']
nosy_count = 4.0
nosy_names = ['barry', 'eli.bendersky', 'ethan.furman', 'edwardw']
pr_nums = ['7950']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue33976'
versions = []

[edwardcwang]

Methods defined in Enums behave 'normally' but classes defined in Enums get mistaken for regular values and can't be used as classes out of the box.

class Outer(Enum):
    a = 1
    b = 2
    class Inner(Enum):
        foo = 10
        bar = 11

[ethanfurman]

Edward, thank you for taking the time to submit a patch, complete with tests!

Do you have a real-world example of why Enum should work this way?

[edwardcwang]

Ethan - thank you for your speedy response!

For an example you can see https://github.com/ucb-bar/hammer/blob/97021bc7e1c819747f8b8b6d4b8c76cdc6a488e3/src/hammer-vlsi/hammer_vlsi_impl.py#L195 - the ObstructionType enum is really only used inside PlacementConstraintType, so it was thought to be logical to nest ObstructionType inside PlacementConstraintType and reference it as PlacementConstraintType.ObstructionType.

It just seemed weird that inline class definitions inside an Enum get treated as an enum value while functions defined inside Enums are treated as methods - as a user it would make more sense to have them both treated the same way (not as enum values), I think.

[ethanfurman]

Edward,

I'm inclined to agree with you. It will take a couple versions for deprecation, etc., to push this through (assuming nobody comes up with a good counter-argument).

In the mean-time, this change has landed in aenum [1] so you can use it now.

[1] https://pypi.org/project/aenum/