Determining common needs in a base class

We first define a directory structure that will contain information pertinent to sweetscomplete. Under this, we create a subdirectory entity where our new base module will be placed. We then create an empty __init__.py file at each directory level to indicate the presence of a Python module. In the entity directory, we create a base.py file to contain our new base class. Eventually, we will also define entity classes for customers, products, and purchases.

The resulting directory structure appears as follows:

/path/to/repo/chapters/04/src/
└── sweetscomplete
    ├── entity
    │   ├── base.py
    │   ├── common.py
    │   ├── customer.py
    │   ├── __init__.py
    │   ├── product.py
    │   └── purchase.py
    └── __init__...