I am working on a python tetris game that my proffessor assigned for the final project of a concepts of programming class. I have got just about everything he wanted to work on it at this point but I am having a slight problem with one part of it. Whenever I start moving pieces left and right I keep getting "index out of range error". This only happens when it is up against a piece. Here are the culprits that are giving me grief. def clearRight(block=None): global board, activeBlock, stackedBlocks isClear = True if(block == None): block = activeBlock if(block != None): for square in block['squares']: row = square[1] col = square[0]+1 if(col >= 0 and stackedBlocks[row][col] !=None): isClear=False return isClear def clearLeft(block=None): global board, activeBlock, stackedBlocks isClear = True if(block == None): block = activeBlock if(block != None): for square in block['squares']: row = square[1] col = square[0]-1 if(col >= 0 and stackedBlocks[row][col] !=None): isClear=False return isClear I am not looking to get anyone to fix it for me, I'm only looking for tips on how to fix it myself. Thanks in advance for any help that is given.