the root.geometry() top-level window method returns strings like "212x128+-9+-8" when the window is located in the top left corner. The documentation only describes geometry strings containing + or - location coordinates. If this is correct behaviour, the documentation should provide a better description of the syntax - perhaps a regular expression such as: "\d+x\d+(\+|-|\+-)\d+(\+|-|\+-)\d+" and some text indicating that a +- coordinate indicates a value to the left of or above the screen.

Tested Linux Mint 18, Python 3.5.3, tkinter 8.6

Behaviour is consistent with python 2.7 Tkinter 8.6