5 Best Ways to Draw a Dot on a Canvas on a Click Event in Tkinter Python

💡 Problem Formulation: You’re building a GUI application using Tkinter in Python and you want to respond to user clicks on a canvas by drawing a dot at the location of the click. The input is a user’s click event, and the desired output is a visual dot placed precisely where the user clicked on the canvas.

Method 1: Using the create_oval() Method

The create_oval() method in Tkinter’s Canvas widget can be used to draw a dot. By specifying the same start and end coordinates, plus a tiny offset, you can produce a dot-like effect, essentially drawing a very small circle.

Here’s an example:

import tkinter as tk

def draw_dot(event):
    canvas.create_oval(event.x - 1, event.y - 1, event.x + 1, event.y + 1, fill='black')

root = tk.Tk()
canvas = tk.Canvas(root, width=400, height=400)
canvas.bind('<Button-1>', draw_dot)
canvas.pack()
root.mainloop()

Output: A dot appears on the canvas where the user clicks.

This snippet sets up a Tkinter window with a Canvas widget. The draw_dot() function is bound to the left mouse click event, so whenever the canvas is clicked, this function is called, drawing a small circle at the coordinates of the click, effectively creating a dot.

Method 2: Customizing Dot Size and Color

To provide a more customizable user experience, you can define additional parameters such as the size and color of the dot. This allows for more flexibility and creative possibilities when drawing on the canvas.

Here’s an example:

import tkinter as tk

def draw_dot(event, radius=5, dot_color='red'):
    canvas.create_oval(event.x - radius , event.y - radius, event.x + radius, event.y + radius, fill=dot_color)

root = tk.Tk()
canvas = tk.Canvas(root, width=400, height=400)
canvas.bind('<Button-1>', lambda e: draw_dot(e, radius=10, dot_color='blue'))
canvas.pack()
root.mainloop()

Output: A blue dot with a larger radius appears on the canvas where the user clicks.

The enlarged dot is a result of the lambda function in the event binding, which passes a larger radius and a different color as arguments to the draw_dot() function, showcasing how to alter the appearance of dots with parameters.

Method 3: Storing Dot Positions

If the application requires remembering where dots have been placed, you can store the positions in a list. This method enables tracking of all drawn dots, which can be useful for undo features, saving drawings, or further processing.

Here’s an example:

import tkinter as tk

dot_positions = []

def draw_dot(event):
    dot_id = canvas.create_oval(event.x - 2, event.y - 2, event.x + 2, event.y + 2, fill='green')
    dot_positions.append((event.x, event.y, dot_id))

root = tk.Tk()
canvas = tk.Canvas(root, width=400, height=400)
canvas.bind('<Button-1>', draw_dot)
canvas.pack()
root.mainloop()

Output: A green dot appears on the canvas where the user clicks, and its position is stored.

When the user clicks on the canvas, a green dot is drawn, and its position together with its canvas item ID is stored in the dot_positions list. This could be used later for additional functionality such as removing the last dot or changing its properties.

Method 4: Interactive Dot Drawing with Dragging

Enhancing the interactivity, this method involves drawing dots not only on click events but also while dragging the mouse across the canvas. It’s suited for creating paths or freehand drawing.

Here’s an example:

import tkinter as tk

def draw_dot(event):
    canvas.create_oval(event.x - 2, event.y - 2, event.x + 2, event.y + 2, fill='purple')

def activate_paint(event):
    canvas.bind('<B1-Motion>', draw_dot)

root = tk.Tk()
canvas = tk.Canvas(root, width=400, height=400)
canvas.bind('<Button-1>', activate_paint)
canvas.pack()
root.mainloop()

Output: A series of purple dots appear on the canvas, following the user’s drag.

Upon clicking and holding the left mouse button, activate_paint() binds the mouse motion to the draw_dot() function. As the user drags the mouse, multiple dots are drawn, simulating a drawing line.

Bonus One-Liner Method 5: Using a Lambda Function

A quick and concise way to draw a dot is by using a lambda function directly in the event binding. This one-liner setup is perfect for simple applications and reduces the amount of code.

Here’s an example:

import tkinter as tk

root = tk.Tk()
canvas = tk.Canvas(root, width=400, height=400)
canvas.bind('<Button-1>', lambda e: canvas.create_oval(e.x - 1, e.y - 1, e.x + 1, e.y + 1))
canvas.pack()
root.mainloop()

Output: A default-colored (black) dot appears on the canvas where the user clicks.

This highly compact piece of code lacks a separate function; instead, it binds a lambda function directly to the click event, which creates a dot at the click’s location on the canvas.

Summary/Discussion

• Method 1: Using create_oval(). Strengths: Simple and direct. Weaknesses: Limited customization without additional parameters.
• Method 2: Customizable Size and Color. Strengths: Flexible and user-friendly. Weaknesses: Slightly more complex code.
• Method 3: Storing Dot Positions. Strengths: Enables advanced features like undoing actions. Weaknesses: Additional overhead to manage the positions list.
• Method 4: Interactive Dragging. Strengths: Increased interactivity for drawing paths. Weaknesses: Can result in performance issues with many dots due to high event frequency.
• Method 5: Lambda One-Liner. Strengths: Shortest and fastest to implement. Weaknesses: Least flexible and harder to extend or modify.