Apparently not the shortest solution but I think it's easy to follow the logic.

```
def isValidSudoku(self, board):
return (self.is_row_valid(board) and
self.is_col_valid(board) and
self.is_square_valid(board))
def is_row_valid(self, board):
for row in board:
if not self.is_unit_valid(row):
return False
return True
def is_col_valid(self, board):
for col in zip(*board):
if not self.is_unit_valid(col):
return False
return True
def is_square_valid(self, board):
for i in (0, 3, 6):
for j in (0, 3, 6):
square = [board[x][y] for x in range(i, i + 3) for y in range(j, j + 3)]
if not self.is_unit_valid(square):
return False
return True
def is_unit_valid(self, unit):
unit = [i for i in unit if i != '.']
return len(set(unit)) == len(unit)
```