[New-bugs-announce] [issue39728] Instantiating enum with invalid value results in ValueError twice

[Jonas Malaco]

New submission from Jonas Malaco <jonas at protocubo.io>:

Trying to instantiate an enum with an invalid value results in "During handling of the above exception, another exception occurred:".


$ cat > test.py << EOF
from enum import Enum

class Color(Enum):
    RED = 1
    GREEN = 2
    BLUE = 3

Color(0)
EOF


$ python --version
Python 3.8.1


$ python test.py
ValueError: 0 is not a valid Color

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "test.py", line 8, in <module>
    Color(0)
  File "/usr/lib/python3.8/enum.py", line 304, in __call__
    return cls.__new__(cls, value)
  File "/usr/lib/python3.8/enum.py", line 595, in __new__
    raise exc
  File "/usr/lib/python3.8/enum.py", line 579, in __new__
    result = cls._missing_(value)
  File "/usr/lib/python3.8/enum.py", line 608, in _missing_
    raise ValueError("%r is not a valid %s" % (value, cls.__name__))
ValueError: 0 is not a valid Color


I think this might be related to 019f0a0cb85e ("bpo-34536: raise error for invalid _missing_ results (GH-9147)"), but I haven't been able to confirm.

----------
components: Library (Lib)
messages: 362496
nosy: jonasmalaco
priority: normal
severity: normal
status: open
title: Instantiating enum with invalid value results in ValueError twice
type: behavior
versions: Python 3.8, Python 3.9

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue39728>
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