[Tutor] Tkinter and after() method

[Alan Gauld]

On 31/01/2023 05:46, Phil wrote:

> This is the analogue dial class as it is at the moment:
> 
> class Dial:
>      def __init__(self, x=60, y=60, size=60):
> 
>          self.x = x  # centre of dial
>          self.y = y
>          self.size = size # the diameter of the dial
> 
>          self.xn = self.x + 1 # the end points of the ticks and pointer
>          self.yn = self.y + 1
> 
>          self.value = 0 # the pointer's value

Where are the methods?
An object that has no operations is just data...

> my_dial = None    # I cannot see an alternative to their use at the moment
> my_canvas = None

Why not make them attributes of your root class?
After all the Root class actually represents your
application does it not?

> class Root(tk.Tk):
>      def __init__(self):
>          super().__init__()
>          self.title("Canvas Template")
> 
>          self.frame = tk.Frame(self, background='cornflowerblue')
>          self.frame.pack(side='top', fill='both', expand=True)
> 
>          global my_frame, my_dial, my_canvas
>          my_frame = self.frame
> 
>          self.canvas = tk.Canvas(
>              self.frame, relief='flat', background='lightgrey')
> 
>          self.canvas.pack(side='top', anchor='center', fill='both',
>                           expand=True, padx=10, pady=10)
> 
>          my_canvas = self.canvas
> 
>          self.quit_button = tk.Button(self, text="Quit", command=self.quit)
>          self.quit_button.pack(side=tk.BOTTOM, anchor='se', padx=10, 
> pady=10)
> 
>          self.dial = dial.Dial(180, 160, 120)
> 
>          my_dial = self.dial
> 
>          draw_dial(self.dial, self.canvas)
> 
>          move_pointer(self.dial, self.canvas)
> 
>          loop()
> 
> 
> def draw_dial(the_dial, canvasName):

Why is this not a method of the dial class. "the_dial" being self...
And canvasName is not really a name but a canvas so why not call it so:

class Dial:

   def __init__(...)...
   def draw(self,aCanvas):...

> def move_pointer(the_dial, canvasName):
>      # this is just a test. In real use the_dial.value woule be supplied 
> with
>      # a value from a serial device

Again a method of dial...

> def drawPointer(x_centre, y_centre, x_end, y_end, fill, canvasName):

Again a Dial method.
The coordinates should be known to the dial hopefully?

> def loop():
>      # again, this only for testing

But could be a method of Root?
Then your globals become
self.my_dial etc.

-- 
Alan G
Author of the Learn to Program web site
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