[Enum] Deprecate member.member access with removal in 3.14

[ethanfurman]

Accessing one enum member from another was originally forbidden, but added later to improve performance (but still warned against in the docs). Those performance issues are no longer a problem, and it is now possible to have deprecation warnings in the code to aid in transitioning away from such usage.

[brandtbucher]

Those performance issues are no longer a problem

As somebody who hasn't been following enum changes very closely: why is this?

[ethanfurman]

Performance timings on my system:

The code

import time
import enum

class Color(enum.Enum):
    RED = "Red"
    BLUE = "Blue"
    GREEN = "Green"
RED, BLUE, GREEN = Color

class FastColor:
    RED = Color.RED
    BLUE = Color.BLUE
    GREEN = Color.GREEN

def f():
    for _ in range(10000000):
        Color.RED
        Color.BLUE
        Color.GREEN

def g():
    for _ in range(10000000):
        FastColor.RED
        FastColor.BLUE
        FastColor.GREEN

def h():
    for _ in range(10000000):
        RED
        BLUE
        GREEN

import timeit
print(round(timeit.timeit('f()', number=1, globals=globals()), 2), end='  ')
print(round(timeit.timeit('g()', number=1, globals=globals()), 2), end='  ')
print(round(timeit.timeit('h()', number=1, globals=globals()), 2), end=' \n\n')

version	enum	"fast" enum	global enum
3.9	2.23	0.78	0.41
3.10	2.68	0.91	0.47
3.11	2.29	0.72	0.21
3.12	2.21	0.62	0.14

The 3.12 timings are with every enum member being accessed via the enum.property descriptor (i.e. no enum members being stored directly in the enum class __dict__).

Out of curiosity I ran the above code with member.member access, both with and without the deprecation warning:

warning	no warning
20.41	4.16

So updating code to be correct will keep performance to 3.11 levels (or better).

[JelleZijlstra]

How are the timings for accessing Color.RED.value affected?

[ethanfurman]

Those performance issues are no longer a problem

As somebody who hasn't been following enum changes very closely: why is this?

I can only imagine it's due to the work you and others have done. I had already noticed this in the other issue when comparing 3.10/3.11/3.12, and I was able to get another slight boost by storing the member directly in the descriptor and avoiding a dict lookup.

[ethanfurman]

How are the timings for accessing Color.RED.value affected?

Some improvement, but I don't think I can take any credit for that (and those timings are not affected by this issue).

version	enum property	simple python descriptor	standard property
3.9	5.96	4.9	2.11
3.10	5.64	5.01	2.18
3.11	3.67	3.46	1.58
3.12	3.03	2.75	0.78

[ethanfurman]

I can make .name and .value normal properties (when no member by the same name exists), but when I tried that they stopped being reported by inspect and so also stopped showing up in pydoc.