turtle — Turtle graphics¶
Turtle graphics is an implementation of the popular geometric drawing tools introduced in Logo, developed by Wally Feurzeig, Seymour Papert and Cynthia Solomon in 1967.
Turtle can draw intricate shapes using programs that repeat simple moves.
In Python, turtle graphics provides a representation of a physical “turtle” (a little robot with a pen) that draws on a sheet of paper on the floor.
It’s an effective and well-proven way for learners to encounter programming concepts and interaction with software, as it provides instant, visible feedback. It also provides convenient access to graphical output in general.
Turtle drawing was originally created as an educational tool, to be used by teachers in the classroom. For the programmer who needs to produce some graphical output it can be a way to do that without the overhead of introducing more complex or external libraries into their work.
Tutorial¶
New users should start here. In this tutorial we’ll explore some of the basics of turtle drawing.
Starting a turtle environment¶
In a Python shell, import all the objects of the turtle module:
If you run into a No module named ‘_tkinter’ error, you’ll have to install the Tk interface package on your system.
Basic drawing¶
Send the turtle forward 100 steps:
You should see (most likely, in a new window on your display) a line drawn by the turtle, heading East. Change the direction of the turtle, so that it turns 120 degrees left (anti-clockwise):
Let’s continue by drawing a triangle:
forward(100) left(120) forward(100)
Notice how the turtle, represented by an arrow, points in different directions as you steer it.
Experiment with those commands, and also with backward() and right() .
Pen control¶
Try changing the color — for example, color(‘blue’) — and width of the line — for example, width(3) — and then drawing again.
You can also move the turtle around without drawing, by lifting up the pen: up() before moving. To start drawing again, use down() .
The turtle’s position¶
Send your turtle back to its starting-point (useful if it has disappeared off-screen):
The home position is at the center of the turtle’s screen. If you ever need to know them, get the turtle’s x-y co-ordinates with:
And after a while, it will probably help to clear the window so we can start anew:
Making algorithmic patterns¶
Using loops, it’s possible to build up geometric patterns:
for steps in range(100): for c in ('blue', 'red', 'green'): color(c) forward(steps) right(30)
— which of course, are limited only by the imagination!
Let’s draw the star shape at the top of this page. We want red lines, filled in with yellow:
Just as up() and down() determine whether lines will be drawn, filling can be turned on and off:
while True: forward(200) left(170) if abs(pos()) 1: break
Finally, complete the filling:
(Note that filling only actually takes place when you give the end_fill() command.)
Explanation¶
The turtle module is an extended reimplementation of the same-named module from the Python standard distribution up to version Python 2.5.
It tries to keep the merits of the old turtle module and to be (nearly) 100% compatible with it. This means in the first place to enable the learning programmer to use all the commands, classes and methods interactively when using the module from within IDLE run with the -n switch.
The turtle module provides turtle graphics primitives, in both object-oriented and procedure-oriented ways. Because it uses tkinter for the underlying graphics, it needs a version of Python installed with Tk support.
The object-oriented interface uses essentially two+two classes:
- The TurtleScreen class defines graphics windows as a playground for the drawing turtles. Its constructor needs a tkinter.Canvas or a ScrolledCanvas as argument. It should be used when turtle is used as part of some application. The function Screen() returns a singleton object of a TurtleScreen subclass. This function should be used when turtle is used as a standalone tool for doing graphics. As a singleton object, inheriting from its class is not possible. All methods of TurtleScreen/Screen also exist as functions, i.e. as part of the procedure-oriented interface.
- RawTurtle (alias: RawPen ) defines Turtle objects which draw on a TurtleScreen . Its constructor needs a Canvas, ScrolledCanvas or TurtleScreen as argument, so the RawTurtle objects know where to draw. Derived from RawTurtle is the subclass Turtle (alias: Pen ), which draws on “the” Screen instance which is automatically created, if not already present. All methods of RawTurtle/Turtle also exist as functions, i.e. part of the procedure-oriented interface.
The procedural interface provides functions which are derived from the methods of the classes Screen and Turtle . They have the same names as the corresponding methods. A screen object is automatically created whenever a function derived from a Screen method is called. An (unnamed) turtle object is automatically created whenever any of the functions derived from a Turtle method is called.
To use multiple turtles on a screen one has to use the object-oriented interface.
In the following documentation the argument list for functions is given. Methods, of course, have the additional first argument self which is omitted here.