Didn't see that, thanks.

...well that's one way to build a dictionary, I suppose...

I like that it's classless.

I wonder if it's slower to concatenate "_" than append "_" on a leftover because the whole string has to be traversed

not an issue: all works perfectly in python 3.6. So that's just your code that isn't correct.

All tests with python 3.6.0 report some similar kind of error.

Traceback (most recent call last):
File "main.py", line 9, in
Test.assert_equals(displayActual(interpreter("eeeeseswswswwwnnnsssssss", 100, 6, 9)), displayExpected("111100\r\n100010\r\n100001\r\n100010\r\n111100\r\n100000\r\n100000\r\n100000\r\n100000"), "Your interpreter should terminate normally and return a representation of the final state of the 2D datagrid when all commands have been considered from left to right even if the number of iterations specified have not been fully performed")
File "/home/codewarrior/setup.py", line 85, in displayActual
return prettyPrint(actual)
File "/home/codewarrior/setup.py", line 72, in prettyPrint
rows = datagrid.split("\r\n")
AttributeError: 'NoneType' object has no attribute 'split'

Thanks for a functional solution. I was struggling with this.