python 3.x - I am getting a list index out of range error -

i working on "connect 4" application, when running function see if there 4 in row error: list index out of range.

if explain me how fix error explain why error such occurring in part of code, appreciated.

i including code module because think should enough cover error.

edit adding code main method show how list constructed. adding exact error. thank input.

traceback (most recent call last): file "connect4alphaupdate1.py", line 164, in main() file "connect4alphaupdate1.py", line 30, in main winner = checkwinnerone(boardstatus) file "connect4alphaupdate1.py", line 106, in checkwinnerone if board[x][y] 1 , board[x][y+1] 1 , board[x][y+2] 1 , board[x][y+3] 1: indexerror: list index out of range

def main(): # local variables playermove = 0 winner = false  # list show board status boardstatus = [[0, 0, 0, 0, 0, 0, 0],                [0, 0, 0, 0, 0, 0, 0],                [0, 0, 0, 0, 0, 0, 0],                [0, 0, 0, 0, 0, 0, 0],                [0, 0, 0, 0, 0, 0, 0],                [0, 0, 0, 0, 0, 0, 0]] # while loop run until there winner while winner false:     displayboard(boardstatus)     playermove = playeronemove()     boardstatus = checkmoveone(boardstatus, playermove)     winner = checkwinnerone(boardstatus)     if winner true:         print('player 1 wins')         sys.exit()     displayboard(boardstatus)     playermove = playertwomove()     boardstatus = checkmovetwo(boardstatus, playermove)     winner = checkwinnertwo(boardstatus)     if winner true:         print('player 2 wins')         sys.exit()   def checkwinnerone(board): # check across y in range(0, rows):     x in range (0, cols -3):         if board[x][y] 1 , board[x+1][y] 1 , board[x+2][y] 1 , board[x+3][y] 1:              return true   # check down x in range (cols):     y in range (rows -3):         if board[x][y] 1 , board[x][y+1] 1 , board[x][y+2] 1 , board[x][y+3] 1:             print('b')             return true   # check diagnol 1 x in range (cols - 3):     y in range(rows -3):         if board[x][y] 1 , board[x+1][y-1] 1 , board[x+2][y-2] 1 , board[x+3][y-3] 1:             return true  # check diagnol 2 x in range (rows - 3):     y in range(cols -3):         if board[x][y] 1 , board[x+1][y+1] 1 , board[x+2][y+2] 1 , board[x+3][y+3] 1:             return true  return false 

it looks diagnol1 part of function has error. iterating 0 rows-3, try access element in y-1 position, -1 in first iteration when y = 0. clearly, accesing -1 index of list gives list index out of range error. (same thing happens y-2, y-3)

solution:

that for loop should go 3 rows