Say you scale your problem up and write a Fortran program to run it on a supercomputer. You can then use that same plotting script, which is independent of the language that created the data.

That's basically it for me. Sometimes, I generate data from some very large programs and it's more practical and scalable to process that data outside of Python. In addition, most often, I put the plots inside of a LaTeX generated report or slides. In gnuplot, I can generate a piece of LaTeX code that will automatically match the fonts when the document changes. Does anyone know if the same functionality can be found in matplotlib or do we have to change the fonts by hand?

If you're using veusz (https://veusz.github.io/) then you can interactively modify your plot, changing the appearance and investigating relationships without writing or rerunning code.

If your code takes a long time to run, you'll have to split your python code into two anyway: one part to do the calculation and the other to plot the results. Otherwise, it would take ages to modify plots.

(I am the author of Veusz)