从多个值python获取枚举名称

Question

I'm trying to get the name of a enum given one of its multiple values:

class DType(Enum):
    float32 = ["f", 8]
    double64 = ["d", 9]

when I try to get one value giving the name it works:

print DType["float32"].value[1]  # prints 8
print DType["float32"].value[0]  # prints f

but when I try to get the name out of a given value only errors will come:

print DataType(8).name
print DataType("f").name

raise ValueError("%s is not a valid %s" % (value, cls. name ))

ValueError: 8 is not a valid DataType

ValueError: f is not a valid DataType

Is there a way to make this? Or am I using the wrong data structure?

Answer 1

The easiest way is to use the aenum library ¹ , which would look like this:

from aenum import MultiValueEnum

class DType(MultiValueEnum):
    float32 = "f", 8
    double64 = "d", 9

and in use:

>>> DType("f")
<DType.float32: 'f'>

>>> DType(9)
<DType.double64: 'd'>

As you can see, the first value listed is the canonical value, and shows up in the repr() .

If you want all the possible values to show up, or need to use the stdlib Enum (Python 3.4+), then the answer found here is the basis of what you want (and will also work with aenum ):

class DType(Enum):
    float32 = "f", 8
    double64 = "d", 9

    def __new__(cls, *values):
        obj = object.__new__(cls)
        # first value is canonical value
        obj._value_ = values[0]
        for other_value in values[1:]:
            cls._value2member_map_[other_value] = obj
        obj._all_values = values
        return obj

    def __repr__(self):
        return '<%s.%s: %s>' % (
                self.__class__.__name__,
                self._name_,
                ', '.join([repr(v) for v in self._all_values]),
                )

and in use:

>>> DType("f")
<DType.float32: 'f', 8>

>>> Dtype(9)
<DType.float32: 'd', 9>

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¹ Disclosure: I am the author of the Python stdlib Enum , the enum34 backport , and the Advanced Enumeration ( aenum ) library.