Phase 9 introduces third-party packages after the Python language and standard-library foundations are complete.
External libraries add a new engineering responsibility: dependency contracts. A program now depends not only on Python, but also on package versions, installation state, release notes, and compatibility boundaries.
✅ Complete
- ✅
pandas: Working with Tabular Data - ✅
openpyxl: Automating Excel Workbooks - ✅
requests: Consuming HTTP APIs - ✅
pytest: Engineering Automated Tests
Published executable examples from this phase use the dependencies declared in requirements-external.txt. Repository CI installs that file before executing approved external-library examples.
The published contracts target pandas 3.0.x, openpyxl 3.1.x, Requests 2.34.x, and pytest 9.1.x. pandas 3.0 supports Python 3.11+, PyPI declares Python 3.8+ for openpyxl 3.1.5, and Requests 2.34.2 plus pytest 9.1.1 require Python 3.10+. This repository validates the examples on Python 3.13.
Phase 9 moved from the Python standard library into four third-party engineering boundaries: tabular-data transformation, Excel workbook automation, HTTP/API clients, and automated testing. Each chapter treats the library as a versioned dependency with explicit behavior, safety, and validation contracts.
The next phase is Phase 10: Practical Projects.