AsciiDoc and reST are just plain text, you can edit with any editor or coding IDE, optional helper tools available for many platforms.
The toolchain you use to "generate the docs" depends on what your target output is. AsciiDoc offers a lot more target paths and is more oriented toward longer, structured texts, including full books. reST itself is really more just the syntax for structuring your inline text, whether in standalone text files or embedded in code - it is used by the Python developers for documenting their codebase. You might want to look at Sphinx, which extends reST to be more structural if you want the larger featureset of AsciiDoc.
In either case anyone wanting to generate "the docs" will need the appropriate tools to do so, and when you say "only have Python installed" that implies to me that you're looking for toolchains based on scripts written only in Python - you don't even want e.g. bash shell scripts? If that's the case I think the answer is "no".
Usually the person or team that writes and maintains the docs generates the target output(s) into format(s) that can be read easily with tools they already have - PDF, straight HTML or compiled HTML_help, these days maybe EPUB/mobi ebooks.
If your goal is for everyone touching the source to be able to contribute to the code, having a lightweight markup like these two will allow for that, as the source files are diff'd via your VCS just like the code. But generating the output formats will require the appropriate toolchain to be set up. IMO this isn't an issue, since the person/team responsible for docs quality and accuracy should be verifying the changes before "publishing" the next version of the finished output formats.
But the source files will remain "living" docs, open to all.
Hope this helps clarify your thinking.