Python total_ordering()

In Python, the total_ordering() decorator from the functools module simplifies the creation of fully ordered classes. By defining the __eq__() method and one additional comparison method (__lt__(), __le__(), __gt__(), or __ge__()), all other rich comparison methods are automatically generated.

This decorator reduces redundant code in custom classes that require complete ordering behavior for comparisons, sorting, and equality checks.

Syntax

from functools import total_ordering

@total_ordering
class ClassName:
  def __eq__(self, other): ...
  def __lt__(self, other): ...

Parameters:

The total_ordering() decorator takes no parameters.

Return value:

Returns a class with the missing comparison methods (__le__, __gt__, and __ge__) automatically added.

Example 1: Numeric Wrapper Class

The following example defines a class that compares wrapped numeric values. Only __eq__() and __lt__() are implemented; the rest are generated automatically:

from functools import total_ordering

@total_ordering
class Number:
  def __init__(self, value):
    self.value = value

  def __eq__(self, other):
    return self.value == other.value

  def __lt__(self, other):
    return self.value < other.value

print(Number(3) < Number(4))
print(Number(5) >= Number(5))
print(Number(7) > Number(1))

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The outout of this code is:

True
True
True

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Example 2: Ordering Strings by Length

This example demonstrates ordering based on string length instead of direct string comparison:

from functools import total_ordering

@total_ordering
class Word:
  def __init__(self, text):
    self.text = text

  def __eq__(self, other):
    return len(self.text) == len(other.text)

  def __lt__(self, other):
    return len(self.text) < len(other.text)

print(Word("apple") < Word("banana"))
print(Word("kiwi") == Word("pear"))
print(Word("grape") > Word("fig"))

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The output of this code is:

True
True
True

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Codebyte Example: Prioritizing Tasks

The following codebyte defines a class where objects are ordered by priority value:

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Higher priority numbers are treated as greater for sorting purposes.