[Python-checkins] bpo-14050: Note that not all data can be sorted (GH-15381) (GH-15395)

[Raymond Hettinger]

https://github.com/python/cpython/commit/cb8de91dadf15925fb95069cb190398e1d485f56
commit: cb8de91dadf15925fb95069cb190398e1d485f56
branch: 3.8
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: Raymond Hettinger <rhettinger at users.noreply.github.com>
date: 2019-08-22T09:39:52-07:00
summary:

bpo-14050: Note that not all data can be sorted (GH-15381) (GH-15395)

(cherry picked from commit 4109263a7edce11194e301138cf66fa2d07f7ce4)

Co-authored-by: Raymond Hettinger <rhettinger at users.noreply.github.com>

files:
M Doc/tutorial/datastructures.rst

diff --git a/Doc/tutorial/datastructures.rst b/Doc/tutorial/datastructures.rst
index 01e437bb5da8..a0d56274fd7e 100644
--- a/Doc/tutorial/datastructures.rst
+++ b/Doc/tutorial/datastructures.rst
@@ -125,6 +125,13 @@ only modify the list have no return value printed -- they return the default
 ``None``. [1]_  This is a design principle for all mutable data structures in
 Python.
 
+Another thing you might notice is that not all data can be sorted or
+compared.  For instance, ``[None, 'hello', 10]`` doesn't sort because
+integers can't be compared to strings and *None* can't be compared to
+other types.  Also, there are some types that don't have a defined
+ordering relation.  For example, ``3+4j < 5+7j`` isn't a valid
+comparison.
+
 
 .. _tut-lists-as-stacks: