Expert Python Programming - Second Edition

System-level environment isolation

In most cases, software implementation can iterate fast because developers reuse a lot of existing components. Don't Repeat Yourself—this is a popular rule and motto of many programmers. Using other packages and modules to include them in the codebase is only a part of that culture. What also can be considered under "reused components" are binary libraries, databases, system services, third-party APIs, and so on. Even whole operating systems should be considered as reused.

Backend services of web-based applications are a great example of how complex such applications can be. The simplest software stack usually consists of a few layers (starting from the lowest):

• A database or other kind of storage
• The application ...