Introduction to Programming Nova SBE · 2026/27

Class 2 — Meet the code

Block 1 · Practical · 2026-09-08

Get it running

Everything today is local — no git, no GitHub. That comes in Class 3.

One change since last week: we use Codex (the ChatGPT desktop app, free plan), not Cursor. Not installed yet? Setup — uv and the app, about 15 minutes. Already on Cursor? Keep it today; everything on the sheet works in either.

  1. Download the ZIP for your group's app from the materials below: splitit.zip or tiny-crm.zip.
  2. Unzip it somewhere you'll find again — a nova folder in Documents.
  3. Open that folder in Codex: Open folder → pick the folder that contains app.py. Codex now calls it a project.
  4. Open a terminal in that folder (Windows: right-click in the folder → Open in Terminal; macOS: type cd, drag the folder into Terminal, Enter), then uv run streamlit run app.py. The first time it downloads Python and the libraries (a minute); then your browser opens on the app. Or ask Codex "Run the app" and approve the command.

Cloned the repo last week instead? That works too.

Folder, project, repository. Three words, one thing on your disk. A folder is what you unzipped. A project is that folder opened in Codex, plus the memory of what you asked about it. A repository is a folder whose history git tracks — yours becomes one in Class 3. One app, one folder, one project; don't rename or move it. The long version is in Setup.

In class

The product tour: the workflow you drew last week, running. Your nouns became data/, your steps became app.py, your decisions became logic.py. Then the folder behind the screens, the six words you need to read it (file, function, call, table, entry point, validation), and the three ways every new engineer answers "where does X happen?": follow the click, search the project for the exact words, ask the AI and verify. In Codex all three go through the chat — the difference is what you ask for: show me, find the text, explain.

Then the question sheet, ONBOARDING.md, inside your folder. Ten questions: six about the code, four about checking the AI. The TA answers one live; your group answers the rest, in the file, with a location for every answer. Question 9 is bug #1 (the 001 file in issues/): reproduce it, find the line, fix it, show the TA before and after.

Homework — before Class 3

  1. Finish the sheet in ONBOARDING.md. Every answer with a location: file and line, or what you clicked. To write in the file, tell Codex what to write under which question, then read the change before accepting it.
  2. Keep the folder. Don't delete or rename it. In Class 3 it becomes a git repository, and your sheet and your bug fix become your first commit.
  3. Every laptop runs the app. Still stuck? Post the error on the Moodle forum with a screenshot.
  4. Read specs/feature-1 in your folder. That's what gets built live in Class 3, with tests and a branch.

The question sheets are below for reference; the one that counts is the ONBOARDING.md inside your own folder.

Materials