Class Enum

Lib/enum.py:1134–1355

Create a collection of name/value pairs. Example enumeration: >>> class Color(Enum): ... RED = 1 ... BLUE = 2 ... GREEN = 3 Access them by: - attribute access: >>> Color.RED - value lookup: >>> Color(1) <C

class Enum(metaclass=EnumType):
    """
    Create a collection of name/value pairs.

    Example enumeration:

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

    Access them by:

    - attribute access:

      >>> Color.RED
      <Color.RED: 1>

    - value lookup:

      >>> Color(1)
      <Color.RED: 1>

    - name lookup:

      >>> Color['RED']
      <Color.RED: 1>

    Enumerations can be iterated over, and know how many members they have:

    >>> len(Color)
    3

    >>> list(Color)
    [<Color.RED: 1>, <Color.BLUE: 2>, <Color.GREEN: 3>]

    Methods can be added to enumerations, and members can have their own
    attributes -- see the documentation for details.
    """

    def __new__(cls, value):
        # all enum instances are actually created during class construction
        # without calling this method; this method is called by the metaclass'
        # __call__ (i.e. Color(3) ), and by pickle
        if type(value) is cls:
            # For lookups like Color(Color.RED)
            return value
        # by-value search for a matching enum member
        # see if it's in the reverse mapping (for hashable values)
        try:
            return cls._value2member_map_[value]
        except KeyError:
            # Not found, no need to do long O(n) search
            pass
        except TypeError:
            # not there, now do long search -- O(n) behavior
            for name, unhashable_values in cls._unhashable_values_map_.items():
                if value in unhashable_values: