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sorting howto: Add clarification on < using __lt__ (#92010)

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slateny 2022-04-29 15:08:07 -07:00 • committed by GitHub
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Doc/howto/sorting.rst
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@ -325,7 +325,7 @@ Odd and Ends
>>> standard_way >>> standard_way
[('red', 1), ('red', 2), ('blue', 1), ('blue', 2)] [('red', 1), ('red', 2), ('blue', 1), ('blue', 2)]
* The sort routines are guaranteed to use :meth:`__lt__` when making comparisons * The sort routines use ``<`` when making comparisons
between two objects. So, it is easy to add a standard sort order to a class by between two objects. So, it is easy to add a standard sort order to a class by
defining an :meth:`__lt__` method: defining an :meth:`__lt__` method:
@ -335,6 +335,9 @@ Odd and Ends
>>> sorted(student_objects) >>> sorted(student_objects)
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)] [('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]
However, note that ``<`` can fall back to using :meth:`__gt__` if
:meth:`__lt__` is not implemented (see :func:`object.__lt__`).
* Key functions need not depend directly on the objects being sorted. A key * Key functions need not depend directly on the objects being sorted. A key
function can also access external resources. For instance, if the student grades function can also access external resources. For instance, if the student grades
are stored in a dictionary, they can be used to sort a separate list of student are stored in a dictionary, they can be used to sort a separate list of student