Advanced Enumerations (compatible with Python's stdlib Enum), NamedTuples, and NamedConstants
aenum includes a Python stdlib Enum-compatible data type, as well as a metaclass-based NamedTuple implementation and a NamedConstant class.
An Enum is a set of symbolic names (members) bound to unique, constant values. Within an enumeration, the members can be compared by identity, and the enumeration itself can be iterated over. If using Python 3 there is built-in support for unique values, multiple values, auto-numbering, and suspension of aliasing (members with the same value are not identical), plus the ability to have values automatically bound to attributes.
A NamedTuple is a class-based, fixed-length tuple with a name for each possible position accessible using attribute-access notation as well as the standard index notation.
A NamedConstant is a class whose members cannot be rebound; it lacks all other Enum capabilities, however; consequently, it can have duplicate values.
Base class for creating NamedTuples, either by subclassing or via it's
functional API.
Constant class for creating groups of constants. These names cannot be rebound to other values.
Base class for creating enumerated constants. See section Enum Functional API
for an alternate construction syntax.
Base class for creating enumerated constants that are also subclasses of int.
Base class for creating enumerated constants that are also subclasses of str.
Derived class that automatically assigns an int value to each member.
Derived class that adds <, <=, >=, and > methods to an Enum.
Derived class that ensures only one name is bound to any one value.
Base class for creating enumerated constants that can be combined using
the bitwise operations without losing their Flag membership.
Base class for creating enumerated constants that can be combined using
the bitwise operators without losing their IntFlag membership.
IntFlag members are also subclasses of int.
Enum class decorator that ensures only one name is bound to any one value.
Descriptor to add constant values to an Enum
Helper to transform target global variables into an Enum.
Helper for specifying keyword arguments when creating Enum members.
Helper for inserting Enum members into a namespace (usually globals()).
Helper for adding new Enum members after creation.
Function to take a Constant or Enum class and insert it into
sys.modules with the effect of a module whose top-level constant and
member names cannot be rebound.
Decorator to force a member in an Enum or Constant.
Decorator to force a normal (non-Enum member) attribute in an Enum
or Constant.
Enumerations can be created using the class syntax, which makes them
easy to read and write. To define an enumeration, subclass Enum as
follows:
>>> from aenum import Enum
>>> class Color(Enum):
... RED = 1
... GREEN = 2
... BLUE = 3
The Enum class is also callable, providing the following functional API:
>>> Animal = Enum('Animal', 'ANT BEE CAT DOG')
>>> Animal
<enum 'Animal'>
>>> Animal.ANT
<Animal.ANT: 1>
>>> Animal.ANT.value
1
>>> list(Animal)
[<Animal.ANT: 1>, <Animal.BEE: 2>, <Animal.CAT: 3>, <Animal.DOG: 4>]
Note that Enum members are boolean True unless the __nonzero__
(Python 2) or __bool__ (Python 3) method is overridden to provide
different semantics.
Flag (and IntFlag) has members that can be combined with each other
using the bitwise operators (&, |, ^, ~). IntFlag members can be combined
with int and other IntFlag members. While it is possible to specify
the values directly it is recommended to use auto as the value and let
(Int)Flag select an appropriate value:
>>> from enum import Flag
>>> class Color(Flag):
... RED = auto()
... BLUE = auto()
... GREEN = auto()
...
>>> Color.RED & Color.GREEN
<Color.0: 0>
>>> bool(Color.RED & Color.GREEN)
False
>>> Color.RED | Color.BLUE
<Color.RED|BLUE: 3>
If you want to name the empty flag, or various combinations of flags, you may:
>>> class Color(Flag):
... BLACK = 0
... RED = auto()
... BLUE = auto()
... GREEN = auto()
... WHITE = RED | BLUE | GREEN
...
>>> Color.BLACK
<Color.BLACK: 0>
>>> Color.WHITE
<Color.WHITE: 7>
Note that (Int)Flag zero-value members have the usual boolean value of
False.
The most common way to create a new NamedTuple will be via the functional API:
>>> from aenum import NamedTuple
>>> Book = NamedTuple('Book', 'title author genre', module=__name__)
The simple method of creating NamedTuples requires always specifying all
possible arguments when creating instances; failure to do so will raise
exceptions.
However, it is possible to specify both docstrings and default values when
creating a NamedTuple using the class method:
>>> class Point(NamedTuple):
... x = 0, 'horizontal coordinate', 0
... y = 1, 'vertical coordinate', 0
...
>>> Point()
Point(x=0, y=0)
Constant is similar to Enum, but does not support the Enum
protocols, and have no restrictions on duplications:
>>> class K(Constant):
... PI = 3.141596
... TAU = 2 * PI
...
>>> K.TAU
6.283192
Detailed documentation can be found at <aenum/doc/aenum.rst>_