Figured I'd post this just in case anyone else is having the same trouble.
When I right-click in some of my Python source files, there is no "Run" command in the right-click context menu. The only way to run the file is by manually creating a run configuration. I think I finally figured out the cause.
The problem seems to be triggered by the presence of any function name that starts with "test". For example, the following function will likely prevent the "Run" command from being available in that file :
I assume the presence of the "test" function causes PyCharm to think that the whole file is a unittest or something.