Automatically create tag after PR based on new version string discovered in source code

Question

I have a Python package hosted on GitHub. My current non-automated workflow is that I

• create a feature branch
• create a PR (on GitHub) feature -> main
• update code (on pushes to the PR branch some CI linting/testing runs)
• Once the update is near completion I
  1. manually version bump __version__ in __init__.py and
  2. manually update CHANGELOG.rst to reflect the new version and changes therein.
• Merge the PR from feature branch into main
• On my local repo, I create a tag on the new commit on the main branch matching the new __version__ in __init__.py. Then I push this tag to GitHub

Could someone point me to/recommend a tool that automates the last step? I've found a number of tools which advertise themselves as parsing the commit logs and source code to infer the next version number and then update it in the source and create a tag. But I don't want the tool to infer the version number and bump it in source + tag, I want it to find the version number in the source and create the tag.