How to Run Javascript from Python?

In Python, we can run Javascript using the PyExecJS library or the js2py library of Python. The PyExecJs library provides a consistent API for running JavaScript code from within Python using a variety of JavaScript engines, including Node.js, JavaScriptCore, and Google's V8 engine. The js2py library allows you to execute JavaScript code from within Python by parsing the JavaScript code and interpreting it in Python. This article will teach us how to run javascript from Python using the PyExecJS library.

Method 1: Using the PyExecJS library

The PyExecJs library provides a simple interface for executing JavaScript code. It allows developers to seamlessly integrate JavaScript functionality within their Python applications. With PyExecJS, users can leverage the power of JavaScript libraries and frameworks without leaving the Python ecosystem.

Installing PyExecJs

Before using the PyExecJs library and we need to install it in our system using the Python package manager. To install the library type the following command in your terminal or command line. Once PyExecJS is installed, you can use the execjs module to execute JavaScript code from within Python

Pip install PyExecJs 

Using PyExecJS to run javascript from Python

JavaScript is primarily used for front-end development, while Python is typically used for back-end development. However, there are times when JavaScript may be necessary for certain tasks on the back end, such as interacting with APIs or performing certain calculations. Python provides a number of tools and libraries that allow you to run JavaScript code from within a Python script.

Example

In the below example, we define some JavaScript code that defines a function to add two numbers together and calls that function with the arguments 2 and 3. We then use the execjs module to execute the JavaScript code and get the result by calling the eval method on the context object returned by execjs.compile. Finally, we print the result.

import execjs

# Define some JavaScript code
js_code = """
function addNumbers(a, b) {
   return a + b;
}

var result = addNumbers(2, 3);
"""

# Use execjs to execute the JavaScript code
ctx = execjs.compile(js_code)

# Get the result of the JavaScript code
result = ctx.eval('result')

# Print the result
print(result)

Output

5

Method 2: Using the js2py library

The js2py is a library that allows you to execute JavaScript code from within Python by parsing the JavaScript code and interpreting it in Python. It is written entirely in Python and does not require any external JavaScript engine to be installed.

Installation

To install the js2py library type the following command in your terminal or command line. Once js2py is installed, you can use the execjs module to execute JavaScript code from within Python

pip install js2py

Example

In the below example, we define some JavaScript code that defines a function to add two numbers together and calls that function with the arguments 2 and 3. We then use the EvalJs class from the js2py library to execute the JavaScript code and get the result by calling the execute method on the context object. Finally, we print the result using a context object.

import js2py

# Define some JavaScript code
js_code = """
function addNumbers(a, b) {
   return a + b;
}

var result = addNumbers(2, 3);
"""

# Use js2py to execute the JavaScript code
context = js2py.EvalJs()
result = context.execute(js_code)

# Print the result
print(context.result)

Output

5

Applications

Running JavaScript code in Python can be useful in various scenarios, some of which are −

• Web Scraping − Web scraping is a process of extracting data from websites. Many websites use JavaScript to dynamically update their content, which can make web scraping more challenging. Running JavaScript code in Python can help overcome this challenge by allowing you to execute the JavaScript code on the webpage and extract the dynamically updated content.

• Server-side Web Development − Node.js is a popular JavaScript runtime built on the V8 engine that allows you to run JavaScript code on the server side. However, if you are already familiar with Python and its libraries, you may want to use Python for server-side web development. Running JavaScript code in Python can help you integrate JavaScript-based libraries and APIs into your Python-based web application.

• Testing − JavaScript is widely used for web development, and Python is widely used for testing. Running JavaScript code in Python can help you automate the testing of JavaScript-based applications by allowing you to execute JavaScript code and test its output.

• Data Science − JavaScript is not commonly used in data science, but it is used for creating interactive visualizations and animations on the web. Running JavaScript code in Python can help you integrate JavaScript-based visualizations and animations into your Python-based data science project.

• Cross-platform Development − JavaScript is commonly used for front-end web development, while Python is commonly used for back-end development and scripting. Running JavaScript code in Python can help you build cross-platform applications that use JavaScript for the front end and Python for the back end.

Conclusion

In this article, we have discussed how we can run a javascript file from Python using the PyExecJS library of Python. These libraries provide a consistent and easy-to-use API for running JavaScript code and can be installed using pip. We can also run javascript code in Python using the js2py library. The js2py library allows you to execute JavaScript code from within Python by parsing the JavaScript code and interpreting it in Python.