diff --git a/Doc/library/turtle.rst b/Doc/library/turtle.rst index a9c0fa96207ae94..a85c3f466323f93 100644 --- a/Doc/library/turtle.rst +++ b/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 ` 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 ` 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 ` + +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 ===========