Initializing the Application Window

The tkinter library provides a standard interface for building desktop applications in Python. Start by initializing the main window with specific dimensions and a title.

import tkinter as tk

root = tk.Tk()
root.title("Python GUI Calculator")
root.geometry("450x400")

Designing the Input Interface

Use Entry widgets to capture user input. Labels help identify where the user should type the numerical values.

header = tk.Label(root, text="Arithmetic Tool\n-----------------", width=20, height=3)
header.pack()

# First Number Input
tk.Label(root, text="Value 1:").place(x=40, y=100)
val1_entry = tk.Entry(root, width=12)
val1_entry.place(x=110, y=100)

# Second Number Input
tk.Label(root, text="Value 2:").place(x=40, y=140)
val2_entry = tk.Entry(root, width=12)
val2_entry.place(x=110, y=140)

Configuring the Result Display

To display the calculated value dynamically, use a DoubleVar linked to a label. This allows the UI to update automatically when the variable's value changes.

calc_result = tk.DoubleVar()
tk.Label(root, text="Calculated Result", font=("Arial", 10, "bold")).place(x=150, y=220)

display_box = tk.Label(root, textvariable=calc_result, width=20, height=4, relief="sunken")
display_box.place(x=130, y=260)

Implementing Calculation Logic

Define functions to perform arithmetic operations. These functions retrieve values from the entry fields, convert them to floats for precision, and update the display variable.

def perform_addition():
    a = float(val1_entry.get())
    b = float(val2_entry.get())
    calc_result.set(a + b)

def perform_subtraction():
    a = float(val1_entry.get())
    b = float(val2_entry.get())
    calc_result.set(a - b)

def perform_multiplication():
    a = float(val1_entry.get())
    b = float(val2_entry.get())
    calc_result.set(a * b)

def perform_division():
    a = float(val1_entry.get())
    b = float(val2_entry.get())
    if b != 0:
        calc_result.set(a / b)
    else:
        calc_result.set(0.0)

Adding Interactive Buttons

Create buttons and assign the logical functions to the command attribute to handle user clicks.

# Action buttons organized by position
btn_add = tk.Button(root, text="Add (+)", width=12, command=perform_addition)
btn_add.place(x=280, y=100)

btn_sub = tk.Button(root, text="Subtract (-)", width=12, command=perform_subtraction)
btn_sub.place(x=280, y=140)

btn_mul = tk.Button(root, text="Multiply (*)", width=12, command=perform_multiplication)
btn_mul.place(x=280, y=180)

btn_div = tk.Button(root, text="Divide (/)", width=12, command=perform_division)
btn_div.place(x=280, y=220)

Complete Implementation

Below is the consolidated code required to run the application.

import tkinter as tk

root = tk.Tk()
root.title("Python GUI Calculator")
root.geometry("450x400")

# UI Headers
header = tk.Label(root, text="Arithmetic Tool\n-----------------", width=20, height=3)
header.pack()

# Input Fields
tk.Label(root, text="Value 1:").place(x=40, y=100)
val1_entry = tk.Entry(root, width=12)
val1_entry.place(x=110, y=100)

tk.Label(root, text="Value 2:").place(x=40, y=140)
val2_entry = tk.Entry(root, width=12)
val2_entry.place(x=110, y=140)

# Output Variable
calc_result = tk.DoubleVar()
tk.Label(root, text="Calculated Result", font=("Arial", 10, "bold")).place(x=150, y=220)
display_box = tk.Label(root, textvariable=calc_result, width=20, height=4, relief="sunken")
display_box.place(x=130, y=260)

# Logic
def perform_addition():
    calc_result.set(float(val1_entry.get()) + float(val2_entry.get()))

def perform_subtraction():
    calc_result.set(float(val1_entry.get()) - float(val2_entry.get()))

def perform_multiplication():
    calc_result.set(float(val1_entry.get()) * float(val2_entry.get()))

def perform_division():
    b = float(val2_entry.get())
    if b != 0:
        calc_result.set(float(val1_entry.get()) / b)

# Buttons
tk.Button(root, text="Add (+)", width=12, command=perform_addition).place(x=280, y=100)
tk.Button(root, text="Subtract (-)", width=12, command=perform_subtraction).place(x=280, y=140)
tk.Button(root, text="Multiply (*)", width=12, command=perform_multiplication).place(x=280, y=180)
tk.Button(root, text="Divide (/)", width=12, command=perform_division).place(x=280, y=220)

root.mainloop()