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That one website that shows how your code runs, one step at a time

Why it's the pick

Paste Python, Java, C, C++ or JavaScript into Python Tutor and step forward and back through each line while it draws your variables, lists, objects and function calls as boxes and arrows. It's free with no account and has been used by over 25 million people, but the visualizer shows ads and works best on short programs.

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2 good alternatives

CS Circles Visualizer cscircles.cemc.uwaterloo.ca University of Waterloo's copy of the Python step-by-step visualizer FreeNo signup Link checked Oct 9
Thonny thonny.org Beginner Python editor that shows each step as code runs FreeNo signupApp download Link checked Oct 9

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