Re: [Edu-sig] some turtle questions
Hi Brian -- If you wanna go to a lot of work, but not a huge amount, write wrapper class for the Standard Library turtle that intercepts its commands and updates an on-board data structure, representing pixels x pixels, specifying self position, keep color info stashed per each one. That's a lot of data, depending on screen resolution. Consider a thick line option if you have one, make your turtle wide body. Or stay with thin. So then if you go turtle.forward(10) you will send it to your self-made forward method. Stop and smell the pixels, see what color was stashed there, either by another turtle (! -- shared data structure) or by this turtle, or maybe it's still the default untrammeled color. You can add new methods, like glide or explode that translate to the underlying turtle somehow -- use your imagination. Kirby On Sun, Jan 24, 2010 at 7:29 AM, Brian Blais bbl...@bryant.edu wrote: Hello, I am trying to think of things to do with the turtle module with my students, and I have some ideas where I am not sure whether the turtle module can do it. 1) is there a way to determine the current screen pixel color? I am thinking about having the turtle go forward until it reaches an object, say a red circle. I can probably do this by making circle objects (drawn with turtles themselves) which know their own position, and check against this info. But I thought it might be useful also for the turtle to know. 2) is there a way to put a limit on the extent the turtle can travel? it seems I can keep moving off of the screen. Is there a way to make it so that a forward(50) command, at the edge, either raises an exception (at the wall) or simply doesn't move the turtle because of the limit? thanks! bb -- Brian Blais bbl...@bryant.edu http://web.bryant.edu/~bblais http://bblais.blogspot.com/ ___ Edu-sig mailing list edu-...@python.org http://mail.python.org/mailman/listinfo/edu-sig -- http://mail.python.org/mailman/listinfo/python-list
Re: [Edu-sig] some turtle questions
I'm almost sure that there's no way for a turtle to know anything about the background. That's an unfortunate limitation! As for putting a limit on a turtle's travel, you need to write an appropriate conditional. For example, if you want your turtle to stay within a 200x200 square centered around the origin and stop if it gets out, do something roughly like: while(math.abs(t.xcor()) 100 and math.abs(t.ycor()) 100): move turtle Of course, you could instead use if statements and simulate bouncing (if my turtle's x coordinate is beyond my bounding box, subtract from its x coordinate). Best, Hélène. Computer Science Teacher Garfield High School http://garfieldcs.com On Sun, Jan 24, 2010 at 7:29 AM, Brian Blais bbl...@bryant.edu wrote: Hello, I am trying to think of things to do with the turtle module with my students, and I have some ideas where I am not sure whether the turtle module can do it. 1) is there a way to determine the current screen pixel color? I am thinking about having the turtle go forward until it reaches an object, say a red circle. I can probably do this by making circle objects (drawn with turtles themselves) which know their own position, and check against this info. But I thought it might be useful also for the turtle to know. 2) is there a way to put a limit on the extent the turtle can travel? it seems I can keep moving off of the screen. Is there a way to make it so that a forward(50) command, at the edge, either raises an exception (at the wall) or simply doesn't move the turtle because of the limit? thanks! bb -- Brian Blais bbl...@bryant.edu http://web.bryant.edu/~bblais http://bblais.blogspot.com/ ___ Edu-sig mailing list edu-...@python.org http://mail.python.org/mailman/listinfo/edu-sig -- http://mail.python.org/mailman/listinfo/python-list
Re: [Edu-sig] some turtle questions
* Helene Martin: I'm almost sure that there's no way for a turtle to know anything about the background. That's an unfortunate limitation! The background for the turtle is just a Tkinter canvas. So yes, it's technically possible to inspect things there, since there is method to obtain the canvas. But unfortunately the canvas is not a bitmapped picture: it just maintains a list of objects to draw (vector graphics, metafile graphics). And so there's no practical way to obtain the current screen pixel color as Brian asks for: there are no pixels in that canvas... Blatant plug: I included some perhaps interesting turtle examples in ch 2 of my writings at url: http://tinyurl.com/programmingbookP3. It starts with some silly figures, then graph drawing, then some recursive figures (idealized tree, C-curve, dragoncurve). Helene: since I'm not on the original list, could you perhaps forward to that list or to the original poster? Thanks, - Alf As for putting a limit on a turtle's travel, you need to write an appropriate conditional. For example, if you want your turtle to stay within a 200x200 square centered around the origin and stop if it gets out, do something roughly like: while(math.abs(t.xcor()) 100 and math.abs(t.ycor()) 100): move turtle Of course, you could instead use if statements and simulate bouncing (if my turtle's x coordinate is beyond my bounding box, subtract from its x coordinate). Best, Hélène. Computer Science Teacher Garfield High School http://garfieldcs.com On Sun, Jan 24, 2010 at 7:29 AM, Brian Blais bbl...@bryant.edu wrote: Hello, I am trying to think of things to do with the turtle module with my students, and I have some ideas where I am not sure whether the turtle module can do it. 1) is there a way to determine the current screen pixel color? I am thinking about having the turtle go forward until it reaches an object, say a red circle. I can probably do this by making circle objects (drawn with turtles themselves) which know their own position, and check against this info. But I thought it might be useful also for the turtle to know. 2) is there a way to put a limit on the extent the turtle can travel? it seems I can keep moving off of the screen. Is there a way to make it so that a forward(50) command, at the edge, either raises an exception (at the wall) or simply doesn't move the turtle because of the limit? thanks! -- http://mail.python.org/mailman/listinfo/python-list
