What's the problem this feature will solve?

This feature request represents support for installing the requirements of a single-file script with inline metadata (PEP 723) using pip.

Pessimistically assuming that this feature request is rejected, this issue is also being filed as a home for a specific record of the maintainer rationale for not including this functionality in pip.

Describe the solution you'd like

I am imagining functionality that would be similar to the existing --requirement argument, with a suitably distinct name to indicate that the metadata format is the one defined by PEP 723 and the living PyPA spec.

Perhaps something like:

$ cat standalone_script.py
# /// script
# requires-python = ">=3.11"
# dependencies = [
#   "requests<3",
#   "rich",
# ]
# ///

import requests
from rich.pretty import pprint

resp = requests.get("https://peps.python.org/api/peps.json")
data = resp.json()
pprint([(k, v["title"]) for k, v in data.items()][:10])

$ pip install --script standalone_script.py
...

Where the pip install invocation is equivalent to pip install "requests<3" "rich" if the requires-python bound is satisfied

Alternative Solutions

I know that other tools¹ in the Python packaging ecosystem do support PEP 723, but these tools are not "included batteries" nearly as often as pip is. In my estimation, supporting in-line metadata in pip will improve the experience of many users (especially non-programmers) who just want to run a script they've been given and are starting with a "typical" bare Python environment.

¹non-exhaustive list: pipx, hatch, pip-run

Additional context

The reference implementation for parsing inline metadata seems to be enough to retrieve the list of requirements from a file. I imagine that the result of this can be plumbed into existing machinery used for satisfying dependencies listed in requirements files.

It's worth mentioning that there is a potential argument for allowing multiple scripts to be parsed and installed from in a single pip invocation (in the same way that --requirement can be given multiple times). I think it makes sense but I can see why there might be some reluctance about doing it since it is more or less directly against the grain of the primary "single script" use-case of inline metadata.

Code of Conduct

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