104 — Logging and Exit Codes

Intermediate

Replace bare print() calls with Python's stdlib logging module to emit structured, level-based output, then use sys.exit() with meaningful non-zero codes so CI/CD pipelines can detect failures automatically.

Learning Objectives

Set up a logger with logging.basicConfig() and logging.getLogger()

Replace diagnostic print() calls with the correct log level: DEBUG, INFO, WARNING, or ERROR

Connect the --verbose flag to DEBUG-level log output

Add a logger.warning() for conditions that need attention but are not failures

Use sys.exit(1) after logger.error() so the process signals failure to the calling shell or pipeline

Test exit codes with shell operators to simulate CI/CD failure detection

Override the log level at runtime using the LOG_LEVEL environment variable

Step 1

Set up the lesson 104 workspace

Create a directory for this lesson, copy `deploy_check.py` from Lesson 103, and confirm the virtual environment is active. Lesson 104 evolves the script by replacing print() with logging and adding explicit sys.exit() calls.

Commands to Run

mkdir -p ~/devops-python/lesson-104

cd ~/devops-python/lesson-104

cp ~/devops-python/lesson-103/deploy_check.py .

source ~/devops-python/lesson-101/devops-env/bin/activate

cat deploy_check.py

What This Does

You are starting from the Lesson 103 version of deploy_check.py, which uses argparse for argument parsing.

By the end of this lesson the script will use the logging module for all diagnostic output and exit with a non-zero code when it encounters an application-level error.

The logging module is part of the Python standard library — no pip install required.

Expected Outcome

Your terminal prompt shows (devops-env). cat deploy_check.py shows the Lesson 103 script: shebang, argparse setup with environment, --format, and --verbose arguments, and print() calls for output.

Pro Tips

1
If you did not complete Lesson 103, copy its final script from the lesson or create `deploy_check.py` with the argparse setup — the exact starting content matters for the later steps.
2
The `source` path assumes the venv is at `~/devops-python/lesson-101/devops-env/`. Adjust if you placed it elsewhere.

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