I was about to open the same issue!  I tend to print nested data structures for debugging; having lists take up a lot of vertical screen estate and leave unused all the horizontal space is an annoyance, so that I regularly have to go back and add the width param.

Contrary to Fred, I think my tools tend to use the available width, but then I think that auto-width is a good behaviour for a tool, but maybe not a good change for a general library.  Raymond’s note about students is also an important point.  I don’t like adding envvars to control the behaviour of a module function at a distance, or magic constants; if I can pass a constant, I can pass a number (for quick debugging) or handle getting the terminal width at a higher layer (in a real command-line program).  For my debugging use case, maybe it’s time I switch to q (on PyPI) and save even more typing.

Even though I was about to request the same feature, I’m now -0.