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I need to reassign the attribute value in Enum.

from enum import Enum class Number(Enum): number = "1" Number.number = "2" # AttributeError: cannot reassign member 'number'

I tried to reassign the attribute, but I got:

AttributeError: cannot reassign member 'number'

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  • 3
    It violates logic of Enum, why do you need to change it? Commented Dec 24, 2022 at 18:33
  • "I need to reassign the attribute value in Enum." Why? What concrete problem do you hope to solve this way? Commented Dec 24, 2022 at 18:35
  • @OlvinRoght have a scenario when I check if the enum value is x, so change it to y Commented Dec 24, 2022 at 18:35
  • @an0ym, Enum is designed to be set of named constants. Logic you described is quite different, maybe you should use simple class? Commented Dec 24, 2022 at 18:37
  • 2
    This is possible but it should never be done in real code. Enumerations, by design, should never have their value changed after the initial definition. Whatever you are trying to achieve should be done in a different way. Commented Dec 24, 2022 at 18:56

4 Answers 4

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Author's note: This is a horrible idea.

Let's just delete the string "1" from Python and replace it with "2"

from ctypes import c_byte from enum import Enum from sys import getsizeof def change_enum_value(old: object, new: object) -> None: """ Assigns contents of new object to old object. The size of new and old objection should be identical. Args: old (Any): Any object new (Any): Any object Raises: ValueError: Size of objects don't match Faults: Segfault: OOB write on destination """ src_s, des_s = getsizeof(new), getsizeof(old) if src_s != des_s: raise ValueError("Size of new and old objects don't match") src_arr = (c_byte * src_s).from_address(id(new)) des_arr = (c_byte * des_s).from_address(id(old)) for index in range(len(des_arr)): des_arr[index] = src_arr[index] class Number(Enum): number = "1" change_enum_value(Number.number.value, "2") print(Number.number.value) # 2

You don't have the "1" anymore, quite literally.

>>> "1" '2' >>>

which sure is a tad concerning...

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Thanks, it's working, but we should change our framework code structure and avoid using the enum if we want to reassign the values.
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If you read the enum Python documentation: The attributes, in your case Number.number, etc., are enumeration members (or members) and are functionally constants.

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@Community ; Link added to the python documentation, thanks!
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When using Enum, your number = "1" is considered as one of the enum entry.

So, firstly, it is thought to be used this way, for example :

from enum import Enum class Number(Enum): numberOne = "1" numberTwo = "2"

By the way, when you access to Number.number, you access to the "enum item", which is more than just the value. The item has, indeed, a name (number) and a value ("1").

So, in theory, the good way to change the value should be :

Number.number.value = "2"

But, in any was, an Enum is made to not be mutable. So you can't do that anyway.

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Conceptually, an Enum is a way to give "nicer names" to "constants" and then use the nicer names in your code rather than using the constants.

This intent is implemented by Python by making the enum members as "functionally constant" ... See Python Enum Documentation.

The names associated with Enums are not like variables.

Hence you cannot change the value of the name.

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