A development version of pipx supports a feature that address this pain point. See pull request #916 [1]

In your script example.py, you would specify your dependencies in a special comment like this:

  # Requirements:
  #     requests
  
  import requests
  ...

Then you could run the script like this:

  pipx run file:example.py

This would install the dependencies in a temporary virtual environment, and run the script in that virtual environment.

[1] https://github.com/pypa/pipx/pull/916