Run a one-file Python script with dependencies: PEP 723 inline metadata + uv run, no venv or requirements.txt

uv init --script fetch.py --python 3.12          # optional scaffold
uv add --script fetch.py 'requests<3' rich       # writes the metadata block
uv run fetch.py

Resulting header (the dependencies field is required even if empty):

#!/usr/bin/env -S uv run --script
# /// script
# requires-python = ">=3.12"
# dependencies = [
#   "requests<3",
#   "rich",
# ]
# ///
import requests

chmod +x fetch.py && ./fetch.py then works directly. Reproducibility: uv lock --script fetch.py writes fetch.py.lock; exclude-newer under [tool.uv] in the block pins resolution to a date. Ad-hoc extra deps without editing: uv run --with httpx fetch.py.