Description

mdboom

opened on Oct 13, 2022

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#30582 (in 3.11) introduced a change to Enum.__str__ so that it shows the enum name and the member name, whereas prior it only included the member name.

This could be a breaking change in some cases. As an example in real world code, the Azure CLI uses enums for the acceptable values of command-line flags, and then uses str on the enum to generate the string that is passed to the subprocess as arguments.

For example, this enum is used to define a "compute model":

class ComputeModelType(str, Enum):

    provisioned = "Provisioned"
    serverless = "Serverless"

And then it's used here to construct arguments for a subprocess:

self.cmd('sql db update -g {} --server {} --name {} --compute-model {}'
                 .format(resource_group, server, database_name, compute_model_serverless),

The changelog entry for this change just says:

IntEnum / IntFlag / StrEnum fixes: these now inherit from ReprEnum so the str() output now matches format() output, which is the data types’ (so both str(AnIntEnum.ONE) and format(AnIntEnum.ONE) is equal to '1').

This is unlikely to be easily findable for users running into this change, since StrEnum doesn't exist in Python 3.10, and it's a little obscure. I would suggest:

The default str() of an Enum has changed to include both Enum name and the member name (Enum.MEMBER), whereas before it was just the member name. To continue to use the old behavior, inherit from IntEnum or StrEnum.

Does this make sense? Are there other cases I'm missing? Happy to file a PR, but thought I would get some discussion first.

Reacted by Jelle Zijlstra

Activity

1. mdboom

   added

   docsDocumentation in the Doc dirDocumentation in the Doc dir

   on Oct 13, 2022
2. mdboom

   changed the title [-]`Enum.__str__` change should be more clear in What's New[/-] [+]`Enum.__str__` change could be improved in What's New[/+] on Oct 13, 2022
3. mdboom

   added

   stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

   3.11only security fixesonly security fixes

   on Oct 13, 2022
4. AlexWaygood

   assigned

   ethanfurman

   on Oct 13, 2022
5. ethanfurman commented on Oct 13, 2022

   

   ethanfurman

   on Oct 13, 2022

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   I'm more than happy to have help crafting a better What's New entry. Keep in mind that the change you are talking about is format, not str -- str() output hasn't changed, format() has changed to match str().
6. mdboom

   added a commit that references this issue on Oct 14, 2022

   pythongh-98250: Improve documentation about change to Enum.__format__

   3cd6e55
7. CAM-Gerlach

   added a commit that references this issue on Oct 15, 2022

   pythongh-98250: Describe __str__/__format__ changes more clearly/accu…

   a596720
8. CAM-Gerlach commented on Oct 15, 2022

   

   CAM-Gerlach

   on Oct 15, 2022

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   Hey, I didn't see this before I first submitted #98295, but I'd noticed something similar, and I've revised that PR to further resolve this issue.
9. ezio-melotti

   closed this as completedin #98295on Oct 18, 2022
10. ezio-melotti

    added a commit that references this issue on Oct 18, 2022

    gh-95913: Copyedit, xref and organize enum section (#98295)

    73e5180
11. miss-islington

    added 2 commits that reference this issue on Oct 18, 2022

    pythongh-95913: Copyedit, xref and organize enum section (pythonGH-98295

    7f8ca17

    gh-95913: Copyedit, xref and organize enum section (GH-98295)

    d798b59
12. CAM-Gerlach

    self-assigned this

    on Oct 18, 2022
13. pablogsal

    added a commit that references this issue on Oct 22, 2022

    gh-95913: Copyedit, xref and organize enum section (GH-98295)

    1f192c3

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