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Update the sorting howto to reflect the PEP 8 advisory to define all six rich comparisons.

This commit is contained in:
Raymond Hettinger 2012-01-10 07:55:17 +00:00
parent cfe6deb6f7
commit c766b31dbc
1 changed files with 7 additions and 3 deletions
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10
Doc/howto/sorting.rst
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@ -276,11 +276,15 @@ Odd and Ends
>>> data = [('red', 1), ('blue', 1), ('red', 2), ('blue', 2)]
>>> assert sorted(data, reverse=True) == list(reversed(sorted(reversed(data))))
* The sort routines are guaranteed to use :meth:`__lt__` when making comparisons
between two objects. So, it is easy to add a standard sort order to a class by
defining an :meth:`__lt__` method::
* To create a standard sort order for a class, just add the appropriate rich
comparison methods:
>>> Student.__eq__ = lambda self, other: self.age == other.age
>>> Student.__ne__ = lambda self, other: self.age != other.age
>>> Student.__lt__ = lambda self, other: self.age < other.age
>>> Student.__le__ = lambda self, other: self.age <= other.age
>>> Student.__gt__ = lambda self, other: self.age > other.age
>>> Student.__ge__ = lambda self, other: self.age >= other.age
>>> sorted(student_objects)
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]