I looked for a #literate_programming tool that is not specific to a single programming language, supports macros (as in one code fragment defines a function with a reference to a statement in its body added by another code fragment, with correct indents for Python), can be easily installed from repos that I already use and does not require TeX output (I hope to post something to that newer thing also called Web). I found exactly #org_mode Babel, it seems to do everything that I need.