Note that there may be times when titles may be substituted, usually for reasons of length, de-clickbating or de-sensationalising, etc. In which case the preferred option is to omit nonessential words or find an alternative, clearer, phrase within the article text itself.
But editorialising, even with relatively innocuous phrases such as "non-painful" is strongly frowned upon.
Therefore, the title should be “gnuplot for numpy.”