025-weather/docs/milestones/mil-004-create-and-export.md

MIL-004: Create and export a DataFrame

Metadata

Key	Value
ID	MIL-004
CrossReference	BC-001
Language	en
Domain	it

Version History

Date	Status	Author	Reviewer	Change	Commit
2026-10-13	Accepted	Jens Tirsvad Nielsen	AI as stand-in for S01	Initial version, reviewed in RC-007 (Go)	165e91a

---

Purpose

This gate decides whether the end of the second lecture is delivered: a DataFrame is created from a dictionary and exported to a CSV file, and the whole lecture can be run with one command that prints each result. The work is delivered on the branch mil-004-create-and-export and one pull request.

Deliverable

src/weather/export.py with create_scores_frame and export_frame, src/weather/__main__.py so that python -m weather prints the results of both lectures, and tests/test_export.py and tests/test_main.py.

Go / No-Go Criteria

#	Criterion (objectively checkable)	Go	No-Go
1	A DataFrame is created from a dictionary	create_scores_frame() has the columns students and scores and the lecture's values	Another shape or values
2	The frame is exported to CSV	export_frame(frame, path) writes the file; reading it back gives an equal frame	The file is missing or the content differs
3	Export never writes where it is not told to	The default file name is new_data.csv from constants.py, written to the path given; tests use only tmp_path	A test writes in the working directory
4	python -m weather prints the lecture's results	Output lists the rows, the temperatures, the average, the maximum, the Monday row, the hottest row and Monday in Fahrenheit; exit code 0	A result is missing or the exit code is not 0
5	The program does not write a file by itself	Running python -m weather in an empty folder leaves it empty, unless the flag --export with a path is given	A file appears without the flag
6	Tests are green	pytest exit code 0	A failing test
7	The code is reviewed	RC-* against QC-PY-001 has the verdict Go	Verdict No-Go or Go-with-conditions

Dependencies

Depends on	Reason
MIL-003 accepted and merged	The program prints what the analysis module computes

Traceability

Business Case objective / KPI / user story	Reference
Objective 7: create and export	BC-001, criterion 6 in Success Criteria
Objective 10: tests with temporary files	BC-001, criterion 7 in Success Criteria

Ownership

Role	Stakeholder ID (SA)
Owner	S01
Approving reviewer	S01

Target Date

2026-10-21 — fourth of five gateways, inside the plan of PP-001 that ends 2026-10-23.

Tasks

#	Task	Summary	Needs its own Use Case/User Story?	Reference
1	Create a DataFrame from a dictionary	Add create_scores_frame() in src/weather/export.py: a dictionary data_dict with students and scores is turned into a DataFrame with pandas.DataFrame, as the lecture does. The values are constants. Serves objective 7.	No
2	Export a DataFrame to a CSV file	Add export_frame(frame, path) that calls DataFrame.to_csv(path); the default name new_data.csv is a constant. Serves objective 7.	No
3	Add the main flow	Add src/weather/__main__.py: print the results of both lectures in the order of the lectures; export only when --export <path> is given. Serves objectives 2 to 7.	No
4	Add the tests for create, export and the main flow	Add tests/test_export.py (round trip through tmp_path) and tests/test_main.py (output of main captured with capsys, nothing written without the flag).	No

---