02_init.md

When using a simple module, we cannot use sub-modules as in numerous packages; for example ma is a sub-module of numpy and we can import it with import numpy.ma.

In WORDIR:

• Create the directory calculator (mkdir calculator)
• Move and rename the module (mv calculator.py calculator/basics.py)
• In the another terminal (with the exported PYTHONPATH), you can import the package with python3 -c "import calculator".
• This technically works but is not exactly what we want. We must create an __init__.py file (touch calculator/__init__.py) so that this directory is fully recognised as a package by python
• We can import basics with python3 -c "import calculator.basics"

Note that you could add subdirectories inside calculator. It is a way of organising your source code by grouping together codes that deal with the same aspect in a directory. If you add a directory named advanced in calculator with the file subtraction.py inside, you can import it by import calculator.advanced.subtraction or from calculator.advanced import subtraction.

Before going any further, we need to commit this first working version to history:

• cd calculator
• git init
• git status
• echo __pycache__ > .gitignore
• git add .gitignore *.py
• git commit

We now have a directory with our source code but where can we put the documentation, the tests, LICENSE...?

Next step here.