python - How to test if an Enum member with a certain name exists?

Question

Using Python 3.4 I want to test whether an Enum class contains a member with a certain name.

Example:

class Constants(Enum):
    One = 1
    Two = 2
    Three = 3

print(Constants['One'])
print(Constants['Four'])

gives:

Constants.One
  File "C:Python34libenum.py", line 258, in __getitem__
    return cls._member_map_[name]
KeyError: 'Four'

I could catch the KeyError and take the exception as indication of existence but maybe there is a more elegant way?

Answer 1

You could use Enum.__members__ - an ordered dictionary mapping names to members:

In [12]: 'One' in Constants.__members__
Out[12]: True

In [13]: 'Four' in Constants.__members__
Out[13]: False