python - 在枚举中搜索值

Question

我是Python新手。我正在尝试检查字符串是否具有枚举中定义的任何匹配值。例如，我想在下面的代码中打印“Found”

我添加了以下隐式方法的定义来支持比较、散列和获取方法

from enum import Enum


class States(Enum):
    COMPLETED_STATE = 'completed'
    DEPENDENCY_WAIT_STATE = 'dependency_wait'
    FAILED_NO_RERUN_STATE = 'failed_no_rerun'
    IGNORED_STATE = 'ignored'
    RUNNING_STATE = 'running'
    NEVER_RUN_STATE = 'never_run'
    ON_HOLD_STATE = 'on_hold'

    def __hash__(self):
        return hash(self.value)

    def __str__(self):
        return self.value

    def __eq__(self, other):
        if type(self) == type(other):
            return self.value == other.value
        return self.value == other

    def __get__(self, *args, **kwargs):
        return self.value


Map = {
    States.ON_HOLD_STATE: [States.NEVER_RUN_STATE],
    States.DISABLED_STATE: [States.NEVER_RUN_STATE],
    States.RUNNING_STATE: [States.DEPENDENCY_WAIT_STATE,
                           States.ON_HOLD_STATE,
                           States.NEVER_RUN_STATE],
    States.IGNORED_STATE: [States.RUNNING_STATE,
                           States.NEVER_RUN_STATE]
}


print(Map[States.RUNNING_STATE]) // ['dependency_wait', 'on_hold', 'never_run']
print(Map['running']) // ['dependency_wait', 'on_hold', 'never_run']
print(States.RUNNING_STATE == 'dependency_wait') // False
print(States.RUNNING_STATE == 'running') // True
print(States.RUNNING_STATE == States.RUNNING_STATE) // True 

if 'running' in States:
    print "Found" // Does not gets printed

if States.RUNNING_STATE in States:
    print "Found here" // Does not gets printed

Answer 1

Enum 的元类 EnumMeta 定义了 __contains__ 魔术方法来测试 Enum 实例是否存在是给定 Enum 类的成员，仅基于成员的名称，而不是值，因此如果您希望它能够基于值测试成员资格，则必须重写 EnumMeta。 __contains__ 具有一个函数，该函数迭代 _member_map_ dict 属性的值并将每个成员值与给定的测试值进行比较，以实现以下目的:

from enum import Enum, EnumMeta

def custom_EnumMeta__contains__(cls, member):
    return isinstance(member, cls) and member.name in cls._member_map_ or \
        any(m._value_ == member for m in cls._member_map_.values())
EnumMeta.__contains__ = custom_EnumMeta__contains__

class States(Enum):
    COMPLETED_STATE = 'completed'
    DEPENDENCY_WAIT_STATE = 'dependency_wait'
    FAILED_NO_RERUN_STATE = 'failed_no_rerun'
    IGNORED_STATE = 'ignored'
    RUNNING_STATE = 'running'
    NEVER_RUN_STATE = 'never_run'
    ON_HOLD_STATE = 'on_hold'

if 'running' in States:
    print "Found"

if States.RUNNING_STATE in States:
    print "Found here"

输出:

Found
Found here