[5.0.x] Updated "Dive Into Python" links.

Backport of 12ffcfc350 from main

docs/intro/contributing.txt

@@ -27,8 +27,8 @@ For this tutorial, we expect that you have at least a basic understanding of
 how Django works. This means you should be comfortable going through the
 existing tutorials on :doc:`writing your first Django app</intro/tutorial01>`.
 In addition, you should have a good understanding of Python itself. But if you
-don't, `Dive Into Python`__ is a fantastic (and free) online book for
-beginning Python programmers.
+don't, `Dive Into Python`_ is a fantastic (and free) online book for beginning
+Python programmers.
 
 Those of you who are unfamiliar with version control systems and Trac will find
 that this tutorial and its links include just enough information to get started.
@@ -45,8 +45,8 @@ so that it can be of use to the widest audience.
     `#django-dev on irc.libera.chat`__ to chat with other Django users who
     might be able to help.
 
-__ https://diveinto.org/python3/table-of-contents.html
 __ https://web.libera.chat/#django-dev
+.. _Dive Into Python: https://diveintopython3.net/
 .. _Django Forum: https://forum.djangoproject.com/
 
 What does this tutorial cover?
@@ -350,7 +350,7 @@ This test checks that the ``make_toast()`` returns ``'toast'``.
     * After reading those, if you want something a little meatier to sink
       your teeth into, there's always the Python :mod:`unittest` documentation.
 
-__ https://diveinto.org/python3/unit-testing.html
+__ https://diveintopython3.net/unit-testing.html
 
 Running your new test
 ---------------------

docs/intro/index.txt

@@ -32,10 +32,12 @@ place: read this material to quickly get up and running.
     `list of Python resources for non-programmers`_
 
     If you already know a few other languages and want to get up to speed with
-    Python quickly, we recommend `Dive Into Python`_. If that's not quite your
-    style, there are many other `books about Python`_.
+    Python quickly, we recommend referring the official
+    `Python documentation`_, which provides comprehensive and authoritative
+    information about the language, as well as links to other resources such as
+    a list of `books about Python`_.
 
     .. _python: https://www.python.org/
     .. _list of Python resources for non-programmers: https://wiki.python.org/moin/BeginnersGuide/NonProgrammers
-    .. _Dive Into Python: https://diveinto.org/python3/table-of-contents.html
+    .. _Python documentation: https://docs.python.org/3/
     .. _books about Python: https://wiki.python.org/moin/PythonBooks