[Tutor] how do i access object

[Kent Johnson]

Ketan Maheshwari wrote:
> Hi All
> I have this code from the web that I modified according to y 
> requirements. It has a class called Circle. Then there are a few objects 
> of this class created using a constructor. The constructor essentially 
> creates the circles and the update mathod makes them move randomly. 
> However, at each updation, I want to access each circle to know its 
> coordinates. At the moment I am not able to do that. I am sure it should 
> be easy to do. Could anyone help me please.

The line
   xy = self.canvas.coords(self.id)
reads the bounding box of the circle. The returned value is a list 
containing the coordinates of the bounding box of the circle (x0, y0, 
x1, y1) - in other words the coordinates of the left, top, right and 
bottom of the circle.

This might help a bit:
http://infohost.nmt.edu/tcc/help/pubs/tkinter/canvas-concepts.html

Kent

> 
> Thanks,
> k.
> 
> Code follows:
> ******************code starts here***************************
> from Tkinter import *
> import time
> import random
> class Circle:
>     def __init__(self, canvas, xy, ink, delta):
>         self.canvas = canvas
>         self.id = self.canvas.create_oval(
>             -15, -15,
>             15, 15,
>             fill=ink
>             )
>        
>         self.canvas.move(self.id, xy[0], xy[1])
>         self.delta = delta
>         self.start = self.move
>      
>     def __call__(self):
>             return self.start # get things going
>     def move(self):
>         rand=random.randint(1,4)
>        
>         if rand==1:
>             xy = self.canvas.coords(self.id)
>             #print xy
>             if xy[2] >= self.canvas.winfo_width():
>                 self.canvas.move(self.id,-self.delta,0)
>             self.canvas.move(self.id,self.delta,0)
>         elif rand==2:
>             xy = self.canvas.coords(self.id)
>             if xy[0] <= 0:
>                 self.canvas.move(self.id,self.delta,0)
>             self.canvas.move(self.id,-self.delta,0)
>         elif rand==3:
>             xy = self.canvas.coords(self.id)
>             if xy[1] <= 0:
>                 self.canvas.move(self.id,0,self.delta)
>             self.canvas.move(self.id,0,-self.delta)
>         else:
>             xy = self.canvas.coords(self.id)
>             if xy[3] >= self.canvas.winfo_height():
>                 self.canvas.move(self.id,0,-self.delta)
>             self.canvas.move(self.id,0,self.delta)
>         return self.move
> 
>        
>    
> root = Tk()
> root.title("Circles")
> root.resizable(0, 0)
> 
> frame = Frame(root, bd=5, relief=SUNKEN)
> frame.pack()
> 
> canvas = Canvas(frame, width=200, height=200, bd=0, highlightthickness=0)
> canvas.pack()
> 
> items = [
>     Circle(canvas, (60, 70), "blue", 1),
>     Circle(canvas, (100, 120), "green", 1),
>     ]
> 
> root.update() # fix geometry
> 
> # loop over items
> 
> try:
>     while 1:
>         for i in range(len(items)):
>             items[i] = items[i]()
>             root.update_idletasks() # redraw
>         root.update() # process events
>         time.sleep(0.02)
> except TclError:
>     pass # to avoid errors when the window is closed
> 
> *************************************code ends 
> here******************************
> _______________________________________________
> Tutor maillist  -  Tutor at python.org
> http://mail.python.org/mailman/listinfo/tutor
> 
>