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Codespace Terminal Procedures -- starting Python, uv, venv, installing dependencies

Step 0 -- This will make your flask app run (but do this after the other steps)

In codespace, the following command will fire up a link that you click on to see your flask app front page.

uv run flask run --host=0.0.0.0 --port=5000

🧭 Step 1 — Install Python (Codespaces base image doesn’t include it)

Run 

sudo apt-get update
sudo apt-get install -y python3 python3-venv python3-pip
Then confirm: 
python3 --version
You should see something like: 
Python 3.12.x

🧭 Step 2 — Install uv (fresh Codespaces never includes it)

Install uv: 

curl -LsSf https://astral.sh/uv/install.sh | sh
Reload your shell so PATH updates: 
source ~/.profile
Confirm: 
uv --version
If that prints a version, uv is ready.

🧭 Step 3 — Create your virtual environment

Your script is correct: it expects .venv to exist. Create it: 

uv venv
Then activate it: 
source .venv/bin/activate
Confirm: 
python --version
which python
You should see .venv/bin/python.

🧭 Step 4 — Sync dependencies

Now install everything from your pyproject.toml: 

uv sync
This installs Flask, SQLAlchemy, your extensions, everything.

🧭 Step 5 — Run your dev-start script again

./scripts/dev-start.sh

Remember

A fresh Codespace:

  • does not include Python
  • does not include uv
  • does not include your .venv
  • does not preserve executable bits on scripts

Your workflow is correct — the environment just needed to be rebuilt.