Question

How can I connect ***kwargs and Canvas?

Posted on August 20, 2023
Community
Asked by tvcsop

How can I connect ***kwargs and Canvas? I studied Digitalocean *args and **kwargs, but this is where I got stuck. What dictionary argument does **kwargs expect? Please help! Thanks!

image alt text

Windows, Python, tkinter, Canvas.

import tkinter as tk

class Sketchpad(tk.Canvas):
    def __init__(self**,** parent**,** **kwargs):
        super().__init__(parent**,** **kwargs)

        self.bind("<Button-1>"**,** self.save_posn)
        self.bind("<B1-Motion>"**,** self.add_line)
        self.lastx**,** self.lasty = **0****,** **0
**        self.color = "black"

        szin_tegla = self.canvas.create_rectangle((**10****,** **10****,** **30****,** **30**)**,** fill="red")
        self.canvas.tag_bind(szin_tegla**,** "<Button-1>"**,** lambda x: self.set_color("red"))

        szin_tegla = self.canvas.create_rectangle((**10****,** **35****,** **30****,** **55**)**,** fill="blue")
        self.canvas.tag_bind(szin_tegla**,** "<Button-1>"**,** lambda x: self.set_color("blue"))

        szin_tegla = self.canvas.create_rectangle((**10****,** **60****,** **30****,** **80**)**,** fill="black")
        self.canvas.tag_bind(szin_tegla**,** "<Button-1>"**,** lambda x: self.set_color("black"))

    def save_posn(self**,** event):
        self.lastx**,** self.lasty = event.x**,** event.y

    def set_color(self**,** newcolor):
        self.color = newcolor

    def add_line(self**,** event):
        self.create_line((self.lastx**,** self.lasty**,** event.x**,** event.y))
        self.save_posn(event)


root = tk.Tk()
root.columnconfigure(**0****,** weight=**1**)
root.rowconfigure(**0****,** weight=**1**)

sketch = Sketchpad(root)
sketch.grid(column=**0****,** row=**0****,** sticky='nwes')

root.mainloop()

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Bobby Iliev

Site Moderator

• August 21, 2023

Accepted Answer

Hi there,

As far as I can tell from the code you provided, there seem to be a few things that might be causing the issue for you:

In the initialization of the Sketchpad class, you are referring to self.canvas, but your Sketchpad class inherits from tk.Canvas. This means self is the canvas. This means that all references to self.canvas should be changed to self.
The **kwargs in your Sketchpad initialization is passed directly to the tk.Canvas’s initialization. This means that any valid Canvas configuration can be passed as keyword arguments when you create a Sketchpad instance.

You can try out the following:

import tkinter as tk

class Sketchpad(tk.Canvas):
    def __init__(self, parent, **kwargs):
        super().__init__(parent, **kwargs)
        
        self.bind("<Button-1>", self.save_posn)
        self.bind("<B1-Motion>", self.add_line)
        self.lastx, self.lasty = 0, 0
        self.color = "black"

        szin_tegla = self.create_rectangle(10, 10, 30, 30, fill="red")
        self.tag_bind(szin_tegla, "<Button-1>", lambda x: self.set_color("red"))

        szin_tegla = self.create_rectangle(10, 35, 30, 55, fill="blue")
        self.tag_bind(szin_tegla, "<Button-1>", lambda x: self.set_color("blue"))

        szin_tegla = self.create_rectangle(10, 60, 30, 80, fill="black")
        self.tag_bind(szin_tegla, "<Button-1>", lambda x: self.set_color("black"))

    def save_posn(self, event):
        self.lastx, self.lasty = event.x, event.y

    def set_color(self, newcolor):
        self.color = newcolor

    def add_line(self, event):
        self.create_line(self.lastx, self.lasty, event.x, event.y, fill=self.color)
        self.save_posn(event)


root = tk.Tk()
root.columnconfigure(0, weight=1)
root.rowconfigure(0, weight=1)

sketch = Sketchpad(root, bg="white", highlightthickness=0)
sketch.grid(column=0, row=0, sticky='nwes')

root.mainloop()

In the code above, when initializing the Sketchpad instance, I added two keyword arguments as an example: bg="white" and highlightthickness=0. This sets the background of the canvas to white and removes the highlight border around the canvas, respectively. This is how you can leverage **kwargs to pass configuration options.

Hope that this helps!

Best,

Bobby