[3.12] gh-106996: Add a how-to section to the turtle documentation (G…

…H-107153) (#107233)

Co-authored-by: Daniele Procida <[email protected]>
Co-authored-by: Hugo van Kemenade <[email protected]>

Doc/library/turtle.rst

@@ -46,6 +46,8 @@ graphical output it can be a way to do that without the overhead of
 introducing more complex or external libraries into their work.
 
 
+.. _turtle-tutorial:
+
 Tutorial
 ========
 
@@ -165,6 +167,118 @@ Finally, complete the filling::
 ``end_fill()`` command.)
 
 
+.. _turtle-how-to:
+
+How to...
+=========
+
+This section covers some typical turtle use-cases and approaches.
+
+
+Get started as quickly as possible
+----------------------------------
+
+One of the joys of turtle graphics is the immediate, visual feedback that's
+available from simple commands - it's an excellent way to introduce children
+to programming ideas, with a minimum of overhead (not just children, of
+course).
+
+The turtle module makes this possible by exposing all its basic functionality
+as functions, available with ``from turtle import *``. The :ref:`turtle
+graphics tutorial <turtle-tutorial>` covers this approach.
+
+It's worth noting that many of the turtle commands also have even more terse
+equivalents, such as ``fd()`` for :func:`forward`. These are especially
+useful when working with learners for whom typing is not a skill.
+
+.. _note:
+
+    You'll need to have the :mod:`Tk interface package <tkinter>` installed on
+    your system for turtle graphics to work. Be warned that this is not
+    always straightforward, so check this in advance if you're planning to
+    use turtle graphics with a learner.
+
+
+Use the ``turtle`` module namespace
+-----------------------------------
+
+Using ``from turtle import *`` is convenient - but be warned that it imports a
+rather large collection of objects, and if you're doing anything but turtle
+graphics you run the risk of a name conflict (this becomes even more an issue
+if you're using turtle graphics in a script where other modules might be
+imported).
+
+The solution is to use ``import turtle`` - ``fd()`` becomes
+``turtle.fd()``, ``width()`` becomes ``turtle.width()`` and so on. (If typing
+"turtle" over and over again becomes tedious, use for example ``import turtle
+as t`` instead.)
+
+
+Use turtle graphics in a script
+-------------------------------
+
+It's recommended to use the ``turtle`` module namespace as described
+immediately above, for example::
+
+    import turtle as t
+    from random import random
+
+    for i in range(100):
+        steps = int(random() * 100)
+        angle = int(random() * 360)
+        t.right(angle)
+        t.fd(steps)
+
+Another step is also required though - as soon as the script ends, Python
+will also close the turtle's window. Add::
+
+    t.mainloop()
+
+to the end of the script. The script will now wait to be dismissed and
+will not exit until it is terminated, for example by closing the turtle
+graphics window.
+
+
+Use object-oriented turtle graphics
+-----------------------------------
+
+.. seealso:: :ref:`Explanation of the object-oriented interface <turtle-explanation>`
+
+Other than for very basic introductory purposes, or for trying things out
+as quickly as possible, it's more usual and much more powerful to use the
+object-oriented approach to turtle graphics. For example, this allows
+multiple turtles on screen at once.
+
+In this approach, the various turtle commands are methods of objects (mostly of
+``Turtle`` objects). You *can* use the object-oriented approach in the shell,
+but it would be more typical in a Python script.
+
+The example above then becomes::
+
+    from turtle import Turtle
+    from random import random
+
+    t = Turtle()
+    for i in range(100):
+        steps = int(random() * 100)
+        angle = int(random() * 360)
+        t.right(angle)
+        t.fd(steps)
+
+    t.screen.mainloop()
+
+Note the last line. ``t.screen`` is an instance of the :class:`Screen`
+that a Turtle instance exists on; it's created automatically along with
+the turtle.
+
+The turtle's screen can be customised, for example::
+
+    t.screen.title('Object-oriented turtle demo')
+    t.screen.bgcolor("orange")
+
+
+.. _turtle-explanation:
+
 Explanation
 ===========