for i in range(len(fenceMap)):
#the same for: for j in fenceMap:
This advice will work in this particular case because the 2D array has the same number of rows and columns, but otherwise it will fail. We have in this level. 8X8 array filled only with 0 and 1. See the visualisation. You can replace arr with arr1 to see how the code works with an “irregular array”.
Edit: @mratranslate : you have similar structure in Power points stuck and you did it right then 