Types of encapsulation

Let’s say you want to move a code from one system to another. What are the things that can go wrong?

• In-language dependencies, e.g. Python. Can they all be expressed only in requirements.txt? Do you wrap everything in a container?

• Paths: Can you always use relative paths?

• Operating-system (OS) dependencies, libraries, etc.: Can you eliminate them?

• Data files: Are they controlled or few that you can migrate, or if you wanted to move it, are you forced to copy the whole directory without regard to what the file is (thus creating a lot of duplicates, and a big mess?)

• Are you using something that is OS-specific (GNU/Linux vs BSD)?

• Do you use support programs only available on certain computers? Fewer external utilities you use = easier portability.

What needs to be global vs what needs to be local?

• Global data can be “seen”/accessed in the entire code.

• Local data is only available in the local vicinity of its definition.

• Try to have as little global data as possible.

• Global data are often input parameters, configuration parameters, command-line arguments.

• But try to localize these to the “main” code/function.