Documentation Link

https://matplotlib.org/devdocs/api/markers_api.html

Problem

• " " or "" are offered for nothing, but with a stem plot, these behave very differently. (The latter draws a connecting line to the marker points.) This is either a matter of missing documentation or a bug in stem.

Suggested improvement

• Clarify the difference between the empty string and a single space (or if that is a bug in stem, fix that bug).
• The choice for "no marker" should have more prominence; it was hard to find. I recommend putting it at the top if possible.
• Markers are used by stem but this is not in the list at the top.