Online Python Tutor is a free educational tool created by Philip Guo !!!
that helps students overcome
a fundamental barrier to learning programming: understanding what happens as the computer executes
each line of a program’s source code.
in the Web browser and visualize what the computer is doing step-by-step as it executes those programs.
Over one million people in over 165 countries have used Online Python Tutor to understand and
debug their programs, often as a supplement to textbooks, lecture notes, and online programming