enumex 3.9

An extension to the standard enum with polymorphism, and abstract methods.

enumex

An extension to the standard enum with polymorphism, and abstract methods.

Install

Python: 3.9.x

Each package version is tightly coupled to the minor Python version. Depending on which Python version your environment is currently using, pip will install the correct package.

pip install enumex

Usage

Importing

EnumEx works alongside the standard library’s enum module.
Use EnumEx from enumex, and auto from enum:

from enumex import EnumEx
from enum import auto

EnumEx Types:

Type	Min Version
EnumEx	all
IntEnumEx	all
FlagEx	all
IntFlagEx	all
StrEnumEx	3.11
ReprEnumEx	3.11

Example

EnumEx behaves like the standard enum, but supports inheritance and abstract enum classes.

from enumex import EnumEx
from enum import auto

class A(EnumEx):
    Val1 = auto()
    Val2 = auto()  

    def print(self):
        print(f"{self.__class__.__name__} {self.name} : {self.value}")

class B(A):
    Val3 = auto()
    Val4 = auto()

print("Printing A...")
for e in A:
    e.print()  

print("\nPrinting B...")
for e in B:
    e.print()

# > Printing A...
# > A Val1 : 1
# > A Val2 : 2
# >
# > Printing B...
# > B Val1 : 1
# > B Val2 : 2
# > B Val3 : 3
# > B Val4 : 4

Abstract Methods

• Defining Abstract Enum Classes
  To define an abstract enum class, you must include ABC as a mixin.
  Using ABCMeta as the metaclass is not enough by itself. EnumExMeta inherits from enum.EnumMeta, and to avoid metaclass conflicts when combining it with ABC, it must also inherit from ABCMeta.
  Because of this, abstract-method enforcement was changed to only activate when the enum actually subclasses ABC.

• Member Access Behavior
  Enum members of an abstract enum (e.g., A.Flag1) are still accessible.
  This is by design: abstractness is enforced only when invoking abstract methods.

• Instantiation Behavior
  Even though calling an enum class (A(1)) normally just performs a member lookup, an exception is still raised when the class is abstract.

from abc import ABC, abstractmethod
from enumex import IntFlagEx
from enum import auto  

class A(ABC, IntFlagEx):
	Flag1 = auto()
	Flag2 = auto()  

	@abstractmethod
	def print(self):
		pass
  
	class B(A):
		Flag3 = auto()
		Flag4 = auto()
  
	def print(self):
		print(f"{self.__class__.__name__} {self.name} : {self.value}")
    
print(f"A(1) = ", end='')
try:
	v  =  A(1)
	print(v)
except  Exception  as  e:
	print(f"Error:", e)  

print(f"B(5) = {B(5):#b}")  
 

print(f"\nA.Flag1 | B.Flag3 = ", end='')
try:
	v = A.Flag1 | B.Flag3 # Attempts to create A instance
	print(v)
except Exception  as  e:
	print(f"Error:", e)

v = B.Flag3 | A.Flag1
print(f"B.Flag3 | A.Flag1 = {v:#b}") 

try:
	print("\nInvoking A.print...")
	for  e  in  A:
		e.print()
except  Exception  as  ex:
	print("Error: ", ex)
  
print("\nManually Printing A...")
for  e  in  A:
	print(f"{e.__class__.__name__}  {e.name} : {e.value}") 

print("\nInvoking B.print...")
for  e  in  B:
	e.print()
  
# > A(1) = Error: ("Can't instantiate abstract class A with abstract method", 'print')
# > B(5) = 0b101
# >
# > A.Flag1 | B.Flag3 = Error: ("Can't instantiate abstract class A with abstract method", 'print')
# > B.Flag3 | A.Flag1 = 0b101
# >
# > Invoking A.print...
# > Error: Cannot call abstract method 'print' on abstract enum 'A'
# >
# > Manually Printing A...
# > A Flag1 : 1
# > A Flag2 : 2
# >
# > Invoking B.print...
# > B Flag1 : 1
# > B Flag2 : 2
# > B Flag3 : 4
# > B Flag4 : 8

License

Python