Re: [Tutor] Tkinter and canvas question

[Phil]

On Mon, 17 Apr 2017 22:57:41 -0500
boB Stepp  wrote:

> I have yet to do much class writing with tkinter, but if I am
> understanding things correctly, in your Sudoku class where you
> instantiate a Canvas instance, you assign it to the name "the_canvas".
> This will be local to the __init__ method's namespace.  I think you
> need to precede each of those "the_canvas" with "self." to get
> "self.the_canvas".  This way your solve method will be able to access
> it.

Thank you Bob. I was fixated on the error being elsewhere and didn't think 
about the_canvas being just another attribute of the class. It seem obvious now 
that I've been shown.

-- 
Regards,
Phil
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Re: [Tutor] Tkinter and canvas question

[Alan Gauld via Tutor]

On 18/04/17 00:13, Phil wrote:
> Thank you for reading this.
> 
> How do I reference the_canvas from my solve() method? 

> class Sudoku(Frame):
> def __init__(self, parent):
> Frame.__init__(self, parent)
> self.parent = parent
> 
> parent.title("Sudoku solver")
> 
>   #create canvas
> the_canvas = Canvas(width = 300, height = 300)
>  
> the_canvas.pack(side = TOP, anchor = NW, padx = 10, pady = 10)

You need to store the_canvas as an instance attribute so you need to
precede it with self:

self.the_canvas = Canvas(width=300, height=300


>   #create grid
> 
> #create solve button
> solve_button = Button(the_canvas, text = "Solve", command = 
> self.solve,
> anchor = W)

Similarly with the button

self.solve_button = 

> solve_button.configure(width = 5, activebackground = "#33B5E5",
> relief = FLAT)
> solve_button.pack(side = TOP)
> solve_button_window = the_canvas.create_window(250, 250, anchor=NW, 
> window=solve_button)

Without the self your widgets are attached to local variables
that go out of scope as soon as init() ends. You could find
them by traversing the child widget tree of self.parent,
but that's just making life difficult for the sake of it!


-- 
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
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Re: [Tutor] Tkinter and canvas question

[boB Stepp]

Sorry for the unnecessary post with no response -- inadvertent click
on "Send" button which was too near Gmail's "..." button to expand
content.

On Mon, Apr 17, 2017 at 6:13 PM, Phil  wrote:
> Thank you for reading this.
>
> How do I reference the_canvas from my solve() method? Despite hours of 
> searching I haven't been able to solve this or find a similar example. All 
> that I've gained is a headache.
>

I have yet to do much class writing with tkinter, but if I am
understanding things correctly, in your Sudoku class where you
instantiate a Canvas instance, you assign it to the name "the_canvas".
This will be local to the __init__ method's namespace.  I think you
need to precede each of those "the_canvas" with "self." to get
"self.the_canvas".  This way your solve method will be able to access
it.

> Exception in Tkinter callback
> Traceback (most recent call last):
>   File "/usr/lib/python3.4/tkinter/__init__.py", line 1536, in __call__
> return self.func(*args)
>   File "/home/pi/sudoku.py", line 64, in solve
> self.the_canvas.create_text(20,20,text="5")
> AttributeError: 'Sudoku' object has no attribute 'the_canvas'
>
> from tkinter import *
>
> class Sudoku(Frame):
> def __init__(self, parent):
> Frame.__init__(self, parent)
> self.parent = parent
>
> parent.title("Sudoku solver")
>
> #create canvas
> the_canvas = Canvas(width = 300, height = 300)
> the_canvas.pack(side = TOP, anchor = NW, padx = 10, pady = 10)
>
> #create grid
>
> #create solve button
> solve_button = Button(the_canvas, text = "Solve", command = 
> self.solve,
> anchor = W)
> solve_button.configure(width = 5, activebackground = "#33B5E5",
> relief = FLAT)
> solve_button.pack(side = TOP)
> solve_button_window = the_canvas.create_window(250, 250, anchor=NW, 
> window=solve_button)
>
> def solve(self):
> print("solve called")
> self.the_canvas.create_text(20,20,text="5")
>
>
> def main():
> root = Tk()
> app = Sudoku(root)
> app.mainloop()
>
> if __name__ == '__main__':
> main()
>
>
> --
> Regards,
> Phil
> ___
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-- 
boB
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Re: [Tutor] Tkinter and canvas question

[boB Stepp]

On Mon, Apr 17, 2017 at 6:13 PM, Phil  wrote:
> Thank you for reading this.
>
> How do I reference the_canvas from my solve() method? Despite hours of 
> searching I haven't been able to solve this or find a similar example. All 
> that I've gained is a headache.
>
> Exception in Tkinter callback
> Traceback (most recent call last):
>   File "/usr/lib/python3.4/tkinter/__init__.py", line 1536, in __call__
> return self.func(*args)
>   File "/home/pi/sudoku.py", line 64, in solve
> self.the_canvas.create_text(20,20,text="5")
> AttributeError: 'Sudoku' object has no attribute 'the_canvas'
>
> from tkinter import *
>
> class Sudoku(Frame):
> def __init__(self, parent):
> Frame.__init__(self, parent)
> self.parent = parent
>
> parent.title("Sudoku solver")
>
> #create canvas
> the_canvas = Canvas(width = 300, height = 300)
> the_canvas.pack(side = TOP, anchor = NW, padx = 10, pady = 10)
>
> #create grid
>
> #create solve button
> solve_button = Button(the_canvas, text = "Solve", command = 
> self.solve,
> anchor = W)
> solve_button.configure(width = 5, activebackground = "#33B5E5",
> relief = FLAT)
> solve_button.pack(side = TOP)
> solve_button_window = the_canvas.create_window(250, 250, anchor=NW, 
> window=solve_button)
>
> def solve(self):
> print("solve called")
> self.the_canvas.create_text(20,20,text="5")
>
>
> def main():
> root = Tk()
> app = Sudoku(root)
> app.mainloop()
>
> if __name__ == '__main__':
> main()
>
>
> --
> Regards,
> Phil
> ___
> Tutor maillist  -  Tutor@python.org
> To unsubscribe or change subscription options:
> https://mail.python.org/mailman/listinfo/tutor



-- 
boB
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[Tutor] Tkinter and canvas question

[Phil]

Thank you for reading this.

How do I reference the_canvas from my solve() method? Despite hours of 
searching I haven't been able to solve this or find a similar example. All that 
I've gained is a headache.

Exception in Tkinter callback
Traceback (most recent call last):
  File "/usr/lib/python3.4/tkinter/__init__.py", line 1536, in __call__
return self.func(*args)
  File "/home/pi/sudoku.py", line 64, in solve
self.the_canvas.create_text(20,20,text="5")
AttributeError: 'Sudoku' object has no attribute 'the_canvas'

from tkinter import *

class Sudoku(Frame):
def __init__(self, parent):
Frame.__init__(self, parent)
self.parent = parent

parent.title("Sudoku solver")

#create canvas
the_canvas = Canvas(width = 300, height = 300)  
   
the_canvas.pack(side = TOP, anchor = NW, padx = 10, pady = 10)

#create grid

#create solve button
solve_button = Button(the_canvas, text = "Solve", command = self.solve,
anchor = W)
solve_button.configure(width = 5, activebackground = "#33B5E5",
relief = FLAT)
solve_button.pack(side = TOP)
solve_button_window = the_canvas.create_window(250, 250, anchor=NW, 
window=solve_button)

def solve(self):
print("solve called")
self.the_canvas.create_text(20,20,text="5")


def main():
root = Tk()
app = Sudoku(root)
app.mainloop()

if __name__ == '__main__':
main()


-- 
Regards,
Phil
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