The variables you define in your Python code has a lexical scope where they are valid. These scopes are categorized as local, enclosing, global and built-in scopes. Python language also provides a few keywords like global and nonlocal to modify the behaviour of its variable name resolution. This video tries to explain how scopes and namespaces work in different scenarios. How variables work in Python: https://www.youtube.com/watch?v=0Om2gYU6clE Credits: The contents of this video are mostly from my notes on Dr. Fred Baptiste's course https://www.udemy.com/course/python-3-deep-dive-part-1/