(It's been three years since a similar question was last asked so I thought I'd see if anything's changed since then.)
I've just completed creating a fairly involved answer, and along the way have created a nice Jupyter notebook (based on Python's symbolic math library SymPy) that would probably be of use to anyone interested in the post, including the O.P. The situation is screaming out for an "Attach file to answer" button, which (unsurprisingly) does not exist. Is the current response still "host it somewhere else on the internet"? I know that the people who will see (and answer) my question probably can't have any influence over what's likely a StackExchange-wide policy, but I gotta note how that's in direct contradiction to the "keep answers self-contained" dictum. Oh well.
And if "host it somewhere" is still the policy, are there any preferred hosts, either (semi-)officially or from users personal experience? It's a 20k text (as opposed to binary) file.