Test your knowledge: Python environment variables

Review

1. Which expression reads an optional environment variable and falls back to "light" when the key is absent?

   os.getenv() returns its default if the named environment variable is absent.
2. A process receives `APP_PORT=8080`. What kind of value does `os.getenv("APP_PORT")` return before conversion?

   Environment-variable values are strings. Convert and validate text before using it as a number or another type.
3. What is the important difference between a missing environment variable and one set to an empty string?

   A present but empty variable produces an empty string. Validate blank values separately when they are not allowed.
4. What must a robust APP_PORT parser do beyond calling `int(raw)`?

   Conversion can fail, and an integer can still be outside the range your application accepts.
5. How should a string setting such as `APP_CACHE="false"` be parsed?

   bool("false") is True because it is a non-empty string. Explicit parsing is predictable and does not execute configuration text.
6. How should a program confirm that an API token setting exists without leaking the secret?

   Environment values should be treated as potentially sensitive input. Avoid writing credentials to logs, output, source control, or examples.