VISUALIZE Python, Java, JavaScript, TypeScript, and Ruby code execution

Online Python Tutor is a free educational tool created by Philip Guo that helps people overcome a fundamental barrier to learning programming: understanding what happens as the computer executes each line of a program’s source code.

Using this tool, you can write Python, Java, JavaScript, TypeScript, and Ruby programs in your Web browser and visualize what the computer is doing step-by-step as it executes those programs.

So far, over 1.2 million people in over 165 countries have used Online Python Tutor to visualize over 11 million pieces of code, often as a supplement to textbooks, lecture notes, and online programming tutorials.

For example, here is a visualization showing a Python program that recursively finds the sum of a linked list. Click the “Forward” button to see what happens as the computer executes each line of code.

Read the research paper – Philip J. Guo. Online Python Tutor: Embeddable Web-Based Program Visualization for CS Education. In Proceedings of the ACM Technical Symposium on Computer Science Education (SIGCSE), March 2013. [BibTeX]