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Functions as Enum member values

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From: colin.mc...@mac.com (Colin McPhail)
Newsgroups: comp.lang.python
Subject: Functions as Enum member values
Date: Mon, 31 May 2021 16:57:00 +0100
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by: Colin McPhail - Mon, 31 May 2021 15:57 UTC

Hi,

According to the enum module's documentation an Enum-based enumeration's members can have values of any type:

"Member values can be anything: int, str, etc.."

I defined one with functions as member values. This seemed to work as long as the functions were defined ahead of the enumeration's definition. However I then noticed that my enumeration class was a bit weird: even although I could reference the enumeration's members individually by name I couldn't iterate through the members in the normal fashion - it seemed to have no members. Also, calling type() on a member gave the result <class 'function'> instead of the expected <enum 'enum name'>.

I am using Python 3.9.5 from python.org on macOS 11.4. Below is a small test script and its output. Are my expectations wrong or is there a problem with Enum?

Regards,
Colin

-------------------------------
from enum import Enum

def connect_impl():
print("message from connect_impl()")

def help_impl():
print("message from help_impl()")

class Command1(Enum):
CONNECT = 1
HELP = 2

class Command2(Enum):
CONNECT = connect_impl
HELP = help_impl

if __name__ == "__main__":

def print_enum(cls, mbr):
print(f"{cls.__name__}\n type(): {type(Command1)}")
print(f" type of enum member: {type(mbr)}")
print(f" number of members: {len(cls)}")
print(" enum members:")
if len(cls) > 0:
for c in cls:
print(f" {c}")
else:
print(" <none>")
print(f" dir(): {dir(cls)}")

member_1 = Command1.HELP
print_enum(Command1, member_1)
print()

member_2 = Command2.HELP
print_enum(Command2, member_2)
print()
print("call Command2 member: ", end="")
member_2()
print()

-------------------------------
(qt6) % python3 try_enum.py
Command1
type(): <class 'enum.EnumMeta'>
type of enum member: <enum 'Command1'>
number of members: 2
enum members:
Command1.CONNECT
Command1.HELP
dir(): ['CONNECT', 'HELP', '__class__', '__doc__', '__members__', '__module__']

Command2
type(): <class 'enum.EnumMeta'>
type of enum member: <class 'function'>
number of members: 0
enum members:
<none>
dir(): ['__class__', '__doc__', '__members__', '__module__']

call Command2 member: message from help_impl()

(qt6) %
-------------------------------

Subject	Author
Functions as Enum member values	Colin McPhail