1 2 3 ---------------------------------------------- 4 5 turtleDemo - Help 6 7 ---------------------------------------------- 8 9 This document has two sections: 10 11 (1) How to use the demo viewer 12 (2) How to add your own demos to the demo repository 13 14 15 (1) How to use the demo viewer. 16 17 Select a demoscript from the example menu. 18 The (syntax colored) source code appears in the left 19 source code window. IT CANNOT BE EDITED, but ONLY VIEWED! 20 21 - Press START button to start the demo. 22 - Stop execution by pressing the STOP button. 23 - Clear screen by pressing the CLEAR button. 24 - Restart by pressing the START button again. 25 26 SPECIAL demos are those which run EVENTDRIVEN. 27 (For example clock.py - or oldTurtleDemo.py which 28 in the end expects a mouse click.): 29 30 Press START button to start the demo. 31 32 - Until the EVENTLOOP is entered everything works 33 as in an ordinary demo script. 34 35 - When the EVENTLOOP is entered, you control the 36 application by using the mouse and/or keys (or it's 37 controlled by some timer events) 38 To stop it you can and must press the STOP button. 39 40 While the EVENTLOOP is running, the examples menu is disabled. 41 42 - Only after having pressed the STOP button, you may 43 restart it or choose another example script. 44 45 * * * * * * * * 46 In some rare situations there may occur interferences/conflicts 47 between events concerning the demo script and those concerning the 48 demo-viewer. (They run in the same process.) Strange behaviour may be 49 the consequence and in the worst case you must close and restart the 50 viewer. 51 * * * * * * * * 52 53 54 (2) How to add your own demos to the demo repository 55 IMPORTANT! When imported, the demo should not modify the system 56 by calling functions in other modules, such as sys, tkinter, or 57 turtle. Global variables should be initialized in main(). 58 59 - The script name must begin with tdemo_ , 60 so it must have the form tdemo_<your-script-name>.py 61 62 - The code must contain a main() function which will 63 be executed by the viewer (see provided example scripts). 64 It may return a string which will be displayed in the Label below 65 the source code window (when execution has finished.) 66 67 - In order to run mydemo.py by itself, such as during development, 68 add the following at the end of the file: 69 70 if __name__ == '__main__': 71 main() 72 mainloop() # keep window 73 74 python -m turtledemo.mydemo # will then run it 75 76 - If the demo is EVENT DRIVEN, main must return the string 77 "EVENTLOOP". This informs the demo viewer that the script is 78 still running and must be stopped by the user! 79 80 If an "EVENTLOOP" demo runs by itself, as with clock, which uses 81 ontimer, or minimal_hanoi, which loops by recursion, then the 82 code should catch the turtle.Terminator exception that will be 83 raised when the user presses the STOP button. (Paint is not such 84 a demo; it only acts in response to mouse clicks and movements.) 85