A module is a function extracted to a file. This allows you to import the function and use it in any other code you may write. You’ll learn how to create modules, import them, and make them stand-alone as you learn what if __name__ == “__main__” means in Python.

If we excute the file in REPL, __bname__ is __main__, if we import the file as module, __name__ is file name.

def total(n):
    tax_rate = .07
    return n * tax_rate + n

def tax_amount(n):
    tax_rate = .07
    return n * tax_rate

# Provide a standalone way for user to use with CMD
# python3 tax.py 10
if __name__ == "__main__":
    import sys
    print(total(int(sys.argv[1])))

[Python] Reuse Code in Multiple Projects with Python Modules