> "uv add"

One life-changing thing I've been using `uv` for:

System python version is 3.12:

    $ python3 --version
    Python 3.12.3

A script that requires a library we don't have, and won't work on our local python:

    $ cat test.py
    #!/usr/bin/env python3

    import sys
    from rich import print

    if sys.version_info < (3, 13):
        print("This script will not work on Python 3.12")
    else:
        print(f"Hello world, this is python {sys.version}")

It fails:

    $ python3 test.py
    Traceback (most recent call last):
    File "/tmp/tmp/test.py", line 10, in <module>
        from rich import print
    ModuleNotFoundError: No module named 'rich'

Tell `uv` what our requirements are

    $ uv add --script=test.py --python '3.13' rich
    Updated `test.py`

`uv` updates the script:

    $ cat test.py
    #!/usr/bin/env python3
    # /// script
    # requires-python = ">=3.13"
    # dependencies = [
    #     "rich",
    # ]
    # ///

    import sys
    from rich import print

    if sys.version_info < (3, 13):
        print("This script will not work on Python 3.12")
    else:
        print(f"Hello world, this is python {sys.version}")

`uv` runs the script, after installing packages and fetching Python 3.13

    $ uv run test.py
    Downloading cpython-3.13.5-linux-x86_64-gnu (download) (33.8MiB)
    Downloading cpython-3.13.5-linux-x86_64-gnu (download)
    Installed 4 packages in 7ms
    Hello world, this is python 3.13.5 (main, Jun 12 2025, 12:40:22) [Clang 20.1.4 ]

And if we run it with Python 3.12, we can see that errors:

    $ uv run --python 3.12 test.py
    warning: The requested interpreter resolved to Python 3.12.3, which is incompatible with the script's Python requirement: `>=3.13`
    Installed 4 packages in 7ms
    This script will not work on Python 3.12

Works for any Python you're likely to want:

    $ uv python list
    cpython-3.14.0b2-linux-x86_64-gnu                 <download available>
    cpython-3.14.0b2+freethreaded-linux-x86_64-gnu    <download available>
    cpython-3.13.5-linux-x86_64-gnu                   /home/dan/.local/share/uv/python/cpython-3.13.5-linux-x86_64-gnu/bin/python3.13
    cpython-3.13.5+freethreaded-linux-x86_64-gnu      <download available>
    cpython-3.12.11-linux-x86_64-gnu                  <download available>
    cpython-3.12.3-linux-x86_64-gnu                   /usr/bin/python3.12
    cpython-3.12.3-linux-x86_64-gnu                   /usr/bin/python3 -> python3.12
    cpython-3.11.13-linux-x86_64-gnu                  /home/dan/.local/share/uv/python/cpython-3.11.13-linux-x86_64-gnu/bin/python3.11
    cpython-3.10.18-linux-x86_64-gnu                  /home/dan/.local/share/uv/python/cpython-3.10.18-linux-x86_64-gnu/bin/python3.10
    cpython-3.9.23-linux-x86_64-gnu                   <download available>
    cpython-3.8.20-linux-x86_64-gnu                   <download available>
    pypy-3.11.11-linux-x86_64-gnu                     <download available>
    pypy-3.10.16-linux-x86_64-gnu                     <download available>
    pypy-3.9.19-linux-x86_64-gnu                      <download available>
    pypy-3.8.16-linux-x86_64-gnu                      <download available>
    graalpy-3.11.0-linux-x86_64-gnu                   <download available>
    graalpy-3.10.0-linux-x86_64-gnu                   <download available>
    graalpy-3.8.5-linux-x86_64-gnu                    <download available>