I installed SAGE mathematics from binary because there was no package for it in synaptic. From reading on the web I learned that SAGE brings its own python libraries rather than using the ones Ubuntu / synaptic has already installed.
I'm getting low on hard disk space -- what can/should I delete? Or how should I rejigger my libraries / system to avoid duplicating ?(gigabytes) worth of libraries?
BTW, I'm having a similar problem with texlive-full -- I first downloaded the package in synaptic, then realised it was outdated, then downloaded the iso -- and now I think I have three or four copies of LaTeX on my drive.
This is one of the downsides of installing software from outside of the standard repositories. For most people, it isn't a big problem, but for you it appears to be an issue due to disk space.
The apps you've downloaded use their own versions of various libraries and software components, and have been tested to work with those components. Removing them will likely cause those programs to be unstable or stop working.
It sounds like you would be safe to remove the texlive-related packages that you've installed via your package manager. That will free up some disk space, as texlive packages are pretty large.
I would recommend:
That will remove the texlive packages you installed, remove any dependencies that are no longer needed, and then clear your cache of packages you previously installed.
As another commenter suggested, though, you might want to consider a backup drive, or (if you can afford it) even a new, larger hard drive. Hard drives are not so expensive these days.