What does it mean to “run library module as a script” with the “-m” option? [duplicate]

Answer 1

This is not a property of python3. You need to use -m in the case of modular script. Say for example you have folder structure like this

|-HelloModule
  |_ __init__.py
  |_ hellomodule.py
|_ first_script.py

Now if you are using any class or function or any object of first_script.py into hellomodule.py then you have to run the hellomodule.py as a module means the command will be changed to

python -m HelloModule/hellomodule

and you have to run this command from the outside of the HelloModule directory.