Simple GUI Calculator using Tkinter

Overview

This is a simple graphical user interface (GUI) calculator built using Python's Tkinter library. It supports basic arithmetic operations: addition (+), subtraction (-), multiplication (*), and division (/). The calculator features a clean interface with numeric buttons, operator buttons, a clear button, and a decimal point button.

Features

• Basic Operations: Perform addition, subtraction, multiplication, and division.
• Error Handling: Displays "Error" for invalid expressions (e.g., division by zero).
• Clear Functionality: Reset the display and expression.
• Chaining Calculations: After evaluating, the result can be used for further operations.
• User-Friendly Interface: Buttons are uniformly styled with red background and black text on a light green window.

Requirements

• Python 3.x
• Tkinter (included with standard Python installations)

How to Run

1. Save the code in a file named simple_calculator.py.
2. Open a terminal or command prompt.
3. Navigate to the directory containing the file.
4. Run the command: python simple_calculator.py.
5. The calculator window will appear.

Usage

• Click numeric buttons (0-9) to input numbers.
• Click operator buttons (+, -, *, /) to input operations.
• Click '.' to add a decimal point.
• Click '=' to evaluate the expression.
• Click 'Clear' to reset the calculator.

Code Explanation

• Class Structure: The calculator logic is encapsulated in a SimpleCalculator class for better organization.
• Display: Uses a StringVar linked to an Entry widget for input/output.
• Buttons: Created dynamically with a helper method _create_button for consistency.
• Expression Handling: Builds an expression string and evaluates it using eval() with basic error catching.
• Layout: Uses grid layout for button placement, with adjusted geometry to fit all elements properly.

Improvements from Original

• Wrapped in a class for modularity and to avoid global variables.
• Adjusted window height to accommodate the decimal button without overlap.
• Added padding to buttons for better spacing.
• Improved error handling to catch all exceptions.
• Allowed result to be used for further calculations (chaining).
• Justified display text to the right for a more natural calculator feel.

Limitations

• Does not support advanced operations like exponents or parentheses.
• Uses eval(), which is simple but not secure for untrusted input (safe here as input is controlled).
• No keyboard input support.