Perform addition and subtraction using CherryPy

CherryPy, a versatile Python web framework, offers a convenient and efficient way to perform addition and subtraction operations. In this article, we delve into the process of utilizing CherryPy to carry out basic arithmetic calculations within a web application.

By leveraging CherryPy's lightweight and intuitive features, developers can effortlessly implement addition and subtraction functionalities, making mathematical operations seamless and easily accessible to users.

Installation

First, install CherryPy using pip ?

pip install cherrypy

Creating a Calculator Web Application

Below are the steps to create a calculator web application with CherryPy ?

• Import the CherryPy module to create a web application.

• Define a class called Calculator with methods for index, add, and subtract.

• The index method serves as the homepage at http://localhost:8080.

• The add and subtract methods are decorated with @cherrypy.expose to make them accessible via URLs.

• Both methods handle error checking for invalid inputs and missing parameters.

Example

import cherrypy

class Calculator:
    @cherrypy.expose
    def index(self):
        return "Welcome to the Calculator!"

    @cherrypy.expose
    def add(self, a=None, b=None):
        if a is not None and b is not None:
            try:
                result = int(a) + int(b)
                return f"The sum of {a} and {b} is: {result}"
            except ValueError:
                return "Invalid input. Please provide valid numbers."
        else:
            return "Please provide two numbers for addition."

    @cherrypy.expose
    def subtract(self, a=None, b=None):
        if a is not None and b is not None:
            try:
                result = int(a) - int(b)
                return f"The difference between {a} and {b} is: {result}"
            except ValueError:
                return "Invalid input. Please provide valid numbers."
        else:
            return "Please provide two numbers for subtraction."

if __name__ == '__main__':
    cherrypy.quickstart(Calculator())

Running the Application

To run the calculator application ?

• Save the code in a Python file, for example, calculator.py.

• Open a terminal and navigate to the directory containing the file.

• Run the program using python calculator.py.

• Open a web browser and visit http://localhost:8080 to see the welcome message.

URL Patterns

Use these URL patterns to perform calculations ?

• Addition: http://localhost:8080/add?a=5&b=3

• Subtraction: http://localhost:8080/subtract?a=8&b=2

Output

When you run the application, the terminal shows ?

C:\Users\Tutorialspoint>python calculator.py
[26/May/2023:16:19:13] ENGINE Listening for SIGTERM.
[26/May/2023:16:19:13] ENGINE Bus STARTING
[26/May/2023:16:19:13] ENGINE Set handler for console events.
[26/May/2023:16:19:13] ENGINE Started monitor thread 'Autoreloader'.
[26/May/2023:16:19:13] ENGINE Serving on http://127.0.0.1:8080
[26/May/2023:16:19:13] ENGINE Bus STARTED

Browser Results

Homepage (http://localhost:8080):

Addition (http://localhost:8080/add?a=5&b=3):

Subtraction (http://localhost:8080/subtract?a=8&b=2):

Key Features

• Error Handling: The application validates input parameters and handles invalid data gracefully.

• URL Parameters: Uses query parameters to pass numbers for calculation.

• Exposed Methods: The @cherrypy.expose decorator makes methods accessible via web URLs.

• Simple Routing: Each method corresponds to a URL endpoint automatically.

Conclusion

CherryPy provides a convenient and efficient solution for performing addition and subtraction operations within web applications. The framework's lightweight design and intuitive routing make it easy to create mathematical web services with proper error handling and user-friendly responses.