Gen-AI Developer Classroom notes 23/Sep/2025

Python modules

• A module is a python file generally ending with .py
• Create a new folder and create two files
  • executable.py
  • library.py
• Generally executable is a program which we run and libraries are also programs which will have reusable stuff.
• To execute a program use python <filename>.py
• To use functions from module into another you can import
• Style 1

import library

library.whoareyou()
print("this is executable")

• Import selectively

from library import whoareyou

whoareyou()
print("this is executable")

• Import with alias

from library import whoareyou as l_whoareyou

def whoareyou():
    print("Im the executable")

whoareyou()
l_whoareyou()

• style guide

dunder means special in python

• In python when we see dunder (double underscores) means it has special functionality

• __name__: This special variable holds the value

  • __main__: when the python code was invoked directy python <filename>.py
  • <module-name>: in the cases of import.

if __name__ == '__main__:
    main()

• Refer Here

Lets build a CLI Enabled Application in python

• This should be calculator

python calc.py add 1 2 
# 3

python calc.py sub 1 2 
# -1

python calc.py mul 1 2 
# 2

# calc.py <operation> <number1> <number2>

• To do this we need to dive into standard library.
• To be discussed in next section