Subtracting gives a keyerror:

[xepicxmonkeyx]

Please post your actual error traceback it is always very important

in addition, just before the line that the code is failing on, add print statements for
all variables that are used in the failing line.

The error is:

Traceback (most recent call last)
   File "python", line 108, in <module>
   File "python", line 92, in switch_target
KeyError: 'Number'

And the print out has been added.