enum34-custom 0.7.2

Custom Enum classes for enum in Python 3.4 or for enum34 for Python2.7

What

Custom Enum classes for the Python 3.4 enum module.

Install

$ pip install enum34-custom

Usage

MultiValueEnum

Enum subclass where a member can be any iterable (even a generator, except str). You can reference a member by any of its element in the associated iterable. It might be usable for e.g. Equivalence Class Partitioning (ECP/EC testing).

from enum_custom import MultiValueEnum

class Suit(MultiValueEnum):
    CLUBS =    '♣', 'c', 'C'
    DIAMONDS = '♦', 'd', 'D'
    HEARTS =   '♥', 'h', 'H'
    SPADES =   '♠', 's', 'S'

>>> print(Suit.CLUBS)
Suit.CLUBS

>>> Suit.CLUBS
<Suit.CLUBS: ('♣', 'c', 'C')>

>>> Suit('c')
<Suit.CLUBS: ('♣', 'c', 'C')>

>>> Suit('c') is Suit('C') is Suit('♣') is Suit.CLUBS
True

>>> import pickle
>>> pickle.loads(pickle.dumps(Suit('c'))) is Suit('♣')
True

>>> Suit('L')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/walkman/Projects/enum34-custom/enum_custom.py", line 19, in __call__
    return super().__call__(suit)
  File "/usr/local/Cellar/python3/3.4.1/Frameworks/Python.framework/Versions/3.4/lib/python3.4/enum.py", line 222, in __call__
    return cls.__new__(cls, value)
  File "/usr/local/Cellar/python3/3.4.1/Frameworks/Python.framework/Versions/3.4/lib/python3.4/enum.py", line 457, in __new__
    raise ValueError("%s is not a valid %s" % (value, cls.__name__))
ValueError: L is not a valid Suit

>>> list(Suit)
[<Suit.CLUBS: ('♣', 'c', 'C')>,
 <Suit.DIAMONDS: ('♦', 'd', 'D')>,
 <Suit.HEARTS: ('♥', 'h', 'H')>,
 <Suit.SPADES: ('♠', 's', 'S')>]

Warning

You need to keep a couple of things in mind when using MultiValueEnum:

• Generators will immediately be exhausted at class creation time!

• To conform to the standard library behavior, overlapping iterables are considered aliases, and works the same way as in stdlib (lookup will match the first declared element):

  >>> class MyOverLappingMVE(MultiValueEnum):
  ...     A = (0, 1, 2, 3, 4)
  ...     B = (4, 5, 6, 7, 8)
  >>> MyOverLappingMVE(4)
  <MyOverLappingMVE.A: (0, 1, 2, 3, 4)>

  If you want to make sure, no overlapping elements are present between members, you can use the no_overlap decorator:

  >>> from enum_custom import MultiValueEnum, no_overlap
  
  >>> @no_overlap
  ... class NoOverLappingEnum(MultiValueEnum):
  ...     A = (1, 2, 3)
  ...     B = (3, 4, 5)
  ...
  /Users/walkman/Projects/enum34-custom/enum_custom.py in no_overlap(multienum)
       55                                   (alias, name, intersection) in duplicates])
       56         raise ValueError('common element found in {!r}: {}'
  ---> 57                          .format(multienum, alias_details))
       58     return multienum
       59
  
  ValueError: common element found in <enum 'NoOverLappingEnum'>: B & A -> {3}

• Beware with storing lots of data, every value will stored twice (MultiValueEnum stores values internally in a set for faster lookups)

• If you declare a dict as a value, keys will be looked up (as expected)

CaseInsensitiveMultiValueEnum

This works the same way as MultiValueEnum except if a member’s value contains a str, those will be compared in a case-insensitive member.

Consider the following example:

class SimpleMultiValueEnum(MultiValueEnum):
    one = 1, 'one'
    two = 2, 'two'

>>> SimpleMultiValueEnum('One')
/usr/local/Cellar/python3/3.4.1_1/Frameworks/Python.framework/Versions/3.4/lib/python3.4/enum.py in __new__(cls, value)
    455                 if member.value == value:
    456                     return member
--> 457         raise ValueError("%s is not a valid %s" % (value, cls.__name__))
    458
    459     def __repr__(self):

ValueError: One is not a valid SimpleMultiValueEnum

While:

class CaseInsensitiveMVE(CaseInsensitiveMultiValueEnum):
    one = 1, 'one'
    two = 2, 'two'

>>> CaseInsensitiveMVE('One')
<CaseInsensitiveMVE.one: (1, 'one')>

StrEnum

Members of this enum are also instances of str and directly comparable to strings. str type is forced at declaration. Works the same way as described in Python Enum documentation, except for checking type.

Warning

It’s not possible to use StrEnum with OrderableMixin, because the members of StrEnum are also instances of str and ordering members will happen beased on str ordering (e.g. ‘1’ < ‘2’, ‘A’ < ‘B’, etc.) If you want ordering by declaration, use OrderableMixin without typed subclass.

CaseInsensitiveStrEnum

Same as StrEnum, but members stored as uppercase, and comparing to them is case insensitive also:

from enum_custom import CaseInsensitiveStrEnum
class MyCaseInsensitiveStrEnum(CaseInsensitiveStrEnum):
    one = 'a'
    two = 'b'

>>> MyCaseInsensitiveStrEnum('a') == 'A'
True
>>> MyCaseInsensitiveStrEnum.one == 'a'
True

Testing

$ python setup.py test

Or install package in development mode and test with py.test:

$ pip install -e .
$ py.test

Differences between Python 2 and 3

There are differences in how Python 2 and 3 creates classes, there are a couple of things that doesn’t work very well on 2, which you should be aware:

• xrange(5) != xrange(5) This is the opposit in Python 3, because range(5) == range(5), however you can use range(5) == range(5) in Python 2 in this case.

• Python 2 have no definition order of members. This means you have to manually define __order__ attribute to be able to compare members by definition order (e.g. with OrderableMixin). See the details in enum34 package dokumentation:

• str vs unicode: This library doesn’t mix and match str types either in Python2 it uses unicode in Python2 and str in Python3 and also enforces the type in StrEnum, CaseInsensitiveStrEnum and ckeck for text type only in CaseInsensitiveMultiValueEnum. (So if you pass str in Python2, it will not be case insensitive!)

• Python 2 leaks variables from list comprehensions, so if you define your class like this:

• On pypy you always have to set __order__ because if you use different types, because it would sort the member values, but can’t compare set to other type.

  class MyList(MultiValueEnum):
      A = [n for n in range(5)]

  MyList will have ‘MyList.n’ also!!!

Changes

v0.7.0

• Python 2.7 support

• Renamed module to enum_custom for consistency (enum34 package is called enum also).