Upendra and Eric: get_list_data() should first parse the string into a list of lines with .splitlines.  At some point, I think the scrolled list should become a scrolled ttk.Treeview, which can have multiple columns.  Then get_line_data should parse each line into name and version.  Then a third column can be added to indicate that a newer version is available.  I wish I had that right now.  I have forgotten how to get the update-available info.

Alexander, the screenshot could not be more timely.  I was thinking of only putting something in the third column when an update is available, but that is a minor detail.

In any case, the point is that the  get_list_data should eventually prepare a package-list-specific list of triples that gets fed to show_list_data.