Class Enum

tables/misc/enum.py:28–427

Enumerated type. Each instance of this class represents an enumerated type. The values of the type must be declared *exhaustively* and named with *strings*, and they might be given explicit concrete values, though this is not compulsory. Once the type is defined, it can not

class Enum:
    """Enumerated type.

    Each instance of this class represents an enumerated type. The
    values of the type must be declared
    *exhaustively* and named with
    *strings*, and they might be given explicit
    concrete values, though this is not compulsory. Once the type is
    defined, it can not be modified.

    There are three ways of defining an enumerated type. Each one
    of them corresponds to the type of the only argument in the
    constructor of Enum:

    - *Sequence of names*: each enumerated
      value is named using a string, and its order is determined by
      its position in the sequence; the concrete value is assigned
      automatically::

          >>> boolEnum = Enum(['True', 'False'])

    - *Mapping of names*: each enumerated
      value is named by a string and given an explicit concrete value.
      All of the concrete values must be different, or a
      ValueError will be raised::

          >>> priority = Enum({'red': 20, 'orange': 10, 'green': 0})
          >>> colors = Enum({'red': 1, 'blue': 1})
          Traceback (most recent call last):
          ...
          ValueError: enumerated values contain duplicate concrete values: 1

    - *Enumerated type*: in that case, a copy
      of the original enumerated type is created. Both enumerated
      types are considered equal::

          >>> prio2 = Enum(priority)
          >>> priority == prio2
          True

    Please note that names starting with _ are
    not allowed, since they are reserved for internal usage::

        >>> prio2 = Enum(['_xx'])
        Traceback (most recent call last):
        ...
        ValueError: name of enumerated value can not start with ``_``: '_xx'

    The concrete value of an enumerated value is obtained by
    getting its name as an attribute of the Enum
    instance (see __getattr__()) or as an item (see
    __getitem__()). This allows comparisons between
    enumerated values and assigning them to ordinary Python
    variables::

        >>> redv = priority.red
        >>> redv == priority['red']
        True