Python Tkinter simple calculator example

Last update on April 25 2025 12:57:30 (UTC/GMT +8 hours)

Write a Python program that implements a simple calculator application using Tkinter with buttons for digits (0-9) and arithmetic operators (+, -, *, /). Implement event handling to calculate.

Sample Solution:

Python Code:

import tkinter as tk
# Function to update the input field
def button_click(char):
    current = entry.get()
    if char == "C":
        entry.delete(0, tk.END)
    elif char == "=":
        try:
            result = eval(current)
            entry.delete(0, tk.END)
            entry.insert(0, result)
        except Exception:
            entry.delete(0, tk.END)
            entry.insert(0, "Error")
    elif char == "←":
        entry.delete(len(current) - 1, tk.END)
    else:
        entry.insert(tk.END, char)

# Create the main window
root = tk.Tk()
root.title("Calculator")

# Create an input field
entry = tk.Entry(root, width=20, font=("Arial", 20))
entry.grid(row=0, column=0, columnspan=5)

# Create buttons for digits (0-9)
buttons = [
    "7", "8", "9", "+",
    "4", "5", "6", "-",
    "1", "2", "3", "*",
    "0", ".", "=", "/"
]
row, col = 1, 0
for button in buttons:
    tk.Button(root, text=button, padx=20, pady=20, font=("Arial", 16),
              command=lambda button=button: button_click(button)).grid(row=row, column=col)
    col += 1
    if col > 3:
        col = 0
        row += 1

# Create a Backspace button
tk.Button(root, text="←", padx=20, pady=20, font=("Arial", 16),
          command=lambda: button_click("←")).grid(row=5, column=3)

# Create a Clear (C) button
tk.Button(root, text="C", padx=20, pady=20, font=("Arial", 16),
          command=lambda: button_click("C")).grid(row=5, column=2)

# Start the Tkinter main loop
root.mainloop()

Explanation:

In the exercise above -

Import the "tkinter" module.
Define functions "button_click(), "clear", and calculate for handling button clicks.
Create the main Tkinter window root and set its title.
Create an input field using 'tk.Entry' for displaying and entering expressions.
Create buttons for digits (0-9) and operators (+, -, *, /) using tk.Button, and we bind the button_click function to each button to update the input field.
Create Clear (C), Equals (=) buttons and add a Backspace (←) button that, when clicked, deletes the last character from the input field. We bind the clear and calculate functions to these buttons.
Finally, start the Tkinter main loop with root.mainloop().

Output:

Flowchart:

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