Advanced Python Calculator with Custom Math Engine

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Project Overview

This is a sophisticated, cross-platform desktop calculator built from the ground up in Python. It serves as a comprehensive portfolio piece demonstrating proficiency in GUI development, advanced software architecture, and secure, robust backend implementation.

Unlike simple calculator scripts, this project features a custom-built mathematical parser and Abstract Syntax Tree (AST) evaluator, eliminating the use of eval() entirely. It also utilizes multi-threading to ensure a fluid, non-blocking user interface.

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Screenshots

Dark Mode	Light Mode	Settings

Calculation Example	Fraction Display	Solver Example

Error Dialog

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Key Technical Features

This project was engineered to professional standards, focusing on security, performance, and user experience.

• Secure Custom Math Engine:
  The core of the application. Instead of using the insecure eval() function, the MathEngine implements its own tokenizer, parser, and Abstract Syntax Tree (AST) builder to safely process, interpret, and compute mathematical expressions.

• Asynchronous & Responsive GUI:
  All calculations are executed in a separate worker thread (QObject worker). This critical design choice ensures the PySide6 main thread remains unblocked, providing a smooth, responsive user experience that never freezes, even during complex computations.

• Integrated Linear Equation Solver:
  The math engine automatically detects expressions containing a variable (e.g., x) and an equals sign. It then traverses the AST to algebraically solve for x, supporting full linear equations (5*x + 10 = 2*x - 2).

• High-Precision & Fraction Arithmetic:
  To ensure mathematical accuracy, the engine uses Python's Decimal module for all calculations, avoiding common floating-point inaccuracies. It also includes support for fractions, displaying results as exact fractions when appropriate.

• Modern Qt6 Interface (PySide6):
  The UI is built with PySide6 (the official Python bindings for Qt 6) and features:

  • A persistent settings dialog to manage application behavior.
  • Full Dark Mode support.
  • An intelligently resizing display font that adapts to long inputs and results.
  • User-friendly features like Undo/Redo, clipboard integration, and button-hold detection.

• Robust Error Handling:
  A custom-defined hierarchy of MathError exceptions (SyntaxError, CalculationError, SolverError) provides clear, user-friendly feedback for invalid syntax, division by zero, or non-linear problems.

• Configuration Management:
  User preferences (like dark mode, decimal places) are saved to an external config.json file and managed by a dedicated config_manager module, demonstrating clean separation of concerns.

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Technology Stack

• GUI: PySide6 (Python for Qt 6)
• Core Logic: Python 3, Decimal, fractions, threading
• Utilities: pyperclip (cross-platform clipboard), pynput (key listener for modifiers like Shift)
• Configuration: json

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Getting Started

Prerequisites

• Python 3.7 or higher
• pip (Python package installer)

Installation & Running

1. Clone the repository:

   git clone https://github.com/JanTeske06/Python_Calculator.git
   cd Python_Calculator

2. Create a virtual environment (Recommended):

   python -m venv venv
   source venv/bin/activate  # On Windows: venv\Scripts\activate

3. Install the required dependencies:

   pip install -r requirements.txt

4. Run the application:

   python main.py

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Project Structure

Python_calculator/
├── Modules/
│   ├── UI.py               # Main GUI class (PySide6 window, widgets, signals)
│   ├── MathEngine.py       # Core engine (Parser, AST, Solver, Evaluator)
│   ├── ScientificEngine.py # Handlers for sin, cos, log, etc.
│   ├── config_manager.py   # Handles loading/saving settings from JSON
│   └── error.py            # Custom error classes and error message dictionary
├── icons/
│   └── icon.png            # Application icon
├── Screenshots/            # Screenshots used in this README
├── config.json             # Stores user settings (persistent)
├── ui_strings.json         # String definitions for the settings UI
├── main.py                 # Application entry point
├── requirements.txt        # Python dependencies
└── README.md               # Readme file

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Acknowledgements

• Special thanks to Julian Theiling for his dedicated bug testing and valuable feedback during development.