Trying to solve one task on 
CodePudding user response：
The error is in is_word(board.copy()[i], word[1:], i, j 1): you pass a list of strings board.copy()[i] as the first parameter instead of a list of lists of strings. Remove the [i].
Trying to solve one task on
CodePudding user response：
The error is in is_word(board.copy()[i], word[1:], i, j 1): you pass a list of strings board.copy()[i] as the first parameter instead of a list of lists of strings. Remove the [i].