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How to compare Enums in Python?

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Table of Contents

How to compare Enums in Python?

  1. How to compare Enums in Python?

    Terrible, horrible, ghastly things can happen with IntEnum. It was mostly included for backwards-compatibility sake, enums used to be implemented by subclassing int.

  2. compare Enums in Python

    Terrible, horrible, ghastly things can happen with IntEnum. It was mostly included for backwards-compatibility sake, enums used to be implemented by subclassing int.

Method 1

You should always implement the rich comparison operaters if you want to use them with an Enum. Using the functools.total_ordering class decorator, you only need to implement an __eq__ method along with a single ordering, e.g. __lt__. Since enum.Enum already implements __eq__ this becomes even easier:

>>> import enum
>>> from functools import total_ordering
>>> @total_ordering
... class Grade(enum.Enum):
...   A = 5
...   B = 4
...   C = 3
...   D = 2
...   F = 1
...   def __lt__(self, other):
...     if self.__class__ is other.__class__:
...       return self.value < other.value
...     return NotImplemented
... 
>>> Grade.A >= Grade.B
True
>>> Grade.A >= 3
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unorderable types: Grade() >= int()

Terrible, horrible, ghastly things can happen with IntEnum. It was mostly included for backwards-compatibility sake, enums used to be implemented by subclassing int.

For the vast majority of code, Enum is strongly recommended, since IntEnum breaks some semantic promises of an enumeration (by being comparable to integers, and thus by transitivity to other unrelated enumerations). It should be used only in special cases where there’s no other choice; for example, when integer constants are replaced with enumerations and backwards compatibility is required with code that still expects integers.

Here’s an example of why you don’t want to do this:

>>> class GradeNum(enum.IntEnum):
...   A = 5
...   B = 4
...   C = 3
...   D = 2
...   F = 1
... 
>>> class Suit(enum.IntEnum):
...   spade = 4
...   heart = 3
...   diamond = 2
...   club = 1
... 
>>> GradeNum.A >= GradeNum.B
True
>>> GradeNum.A >= 3
True
>>> GradeNum.B == Suit.spade
True
>>> 

Method 2

>>> class Grade(OrderedEnum):
...     A = 5
...     B = 4
...     C = 3
...     D = 2
...     F = 1
...
>>> Grade.C < Grade.A
True

Summery

It’s all About this issue. Hope all Methods helped you a lot. Comment below Your thoughts and your queries. Also, Comment below which Method worked for you? Thank You.

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