How to get back name of the enum element?

Question

I have an enum defined like this:

def enum(**enums):
    return type('Enum', (), enums)

Status = enum(
       STATUS_OK=0,
       STATUS_ERR_NULL_POINTER=1, 
       STATUS_ERR_INVALID_PARAMETER=2)

I have a function that returns status as Status enum. How can I get the name of the enum value, and not just value?

>>> cur_status = get_Status()
>>> print(cur_status)
1

I would like to get STATUS_ERR_NULL_POINTER, instead of 1

**Note**: if Python standard library's `enum.Enum` is used, refer to this question → [How to convert int to Enum in python? - Stack Overflow](https://stackoverflow.com/questions/23951641/how-to-convert-int-to-enum-in-python) — user202729, Nov 19 '22 at 12:40

Martijn Pieters · Answer 1 · 2018-09-13T22:19:40.490

You'd have to loop through the class attributes to find the matching name:

name = next(name for name, value in vars(Status).items() if value == 1)

The generator expression loops over the attributes and their values (taken from the dictionary produced by the vars() function) then returns the first one that matches the value 1.

Enumerations are better modelled by the enum library, available in Python 3.4 or as a backport for earlier versions:

from enum import Enum

class Status(Enum):
    STATUS_OK = 0
    STATUS_ERR_NULL_POINTER = 1 
    STATUS_ERR_INVALID_PARAMETER = 2

giving you access to the name and value:

name = Status(1).name  # gives 'STATUS_ERR_NULL_POINTER'
value = Status.STATUS_ERR_NULL_POINTER.value  # gives 1

gerardw · Answer 2 · 2021-03-19T11:51:15.783

56

2021 update: These answers are out of date. Using Python's standard Enum class,

cur_status.name

will return the name. (STATUS_ERR_NULL_POINTER)

To look up the enum knowing the name:

s = Status['STATUS_ERR_NULL_POINTER']

edited Mar 19 '21 at 11:51

answered Mar 17 '21 at 13:19

gerardw

5,822
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2

The question is not about Python's `Enum`, but one the OP created. – Ethan Furman Mar 18 '21 at 01:27
17

OP should be using Python's enum :) – brandonscript Apr 16 '21 at 18:35
This answer does not address the OP's original question, where only the value (`1`) is given instead of the enumeration object, so `(1).name` is invalid. (although it appears useful to some other people). – user202729 Nov 19 '22 at 12:41

score 3 · Answer 3 · answered May 08 '20 at 07:52

3

You don't need to loop through the Enum class but just access _member_map_.

>>> Status._member_map_['STATUS_OK']
<Status.STATUS_OK: 0>

answered May 08 '20 at 07:52

techneer

147
1
6

The question was to find an enum by value (in your example `0`) – Nerman Aug 27 '20 at 11:26
1

This is useful but backwards :) – interestedparty333 Nov 09 '20 at 23:39
The question is not about Python's `Enum`, but one the OP created. – Ethan Furman Mar 18 '21 at 01:27

score 3 · Answer 4 · answered Oct 24 '20 at 00:16

3

Not sure which python version it was introduced, but the hidden attribute _value2member_map_ gives you what you want.

class Status(Enum):
    STATUS_OK=0
    STATUS_ERR_NULL_POINTER=1
    STATUS_ERR_INVALID_PARAMETER=2

str(Status._value2member_map_[1])

Out:

'Status.STATUS_ERR_NULL_POINTER'

answered Oct 24 '20 at 00:16

DeusXMachina

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1
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15

You could simply use `Status(1).name` – Merlin1896 Jan 18 '21 at 10:33
Oh, that is much simpler! – DeusXMachina Jan 18 '21 at 14:02
1

The question is not about Python's `Enum`, but one the OP created. – Ethan Furman Mar 18 '21 at 01:27

score 0 · Answer 5 · answered Jun 09 '21 at 21:57

For some reason, most of the methods above did not work for me. All methods return the Enum type as an integer. I'm working with Python 3.7.

In my solution, I defined class function to handle this. It's not purely pythonic, but worked well enough for my case.

from enum import Enum
    
class Status(Enum):
    STATUS_OK = 0
    STATUS_ERR_NULL_POINTER = 1 
    STATUS_ERR_INVALID_PARAMETER = 2
    
    @classmethod
    def name(cls,val):
        return { v:k for k,v in dict(vars(cls)).items() if isinstance(v,int)}.get(val,None)

# test it
stat = Status.STATUS_OK
print(Status.name(stat))

Prints: 'STATUS_OK'

It may seem obvious that we asked for the status after giving it the status, but in my case, this is set programmatically elsewhere

How to get back name of the enum element?

5 Answers5

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