Validation checking

[Help_me_Please]

Can I please have some help, I am passing in variables correctly and I am trying to check if the column is within the correct table (6 by 6) and I am returning board but the error I get is this:

line 29, in <module>
is_valid_location(board, column, invalid)
NameError: name 'board' is not defined

turn = 0
row = 6
columns = 6
invalid = True
game_over = False

def board_create(columns, row):
    board = [[' '] * columns for row in range(row)]
    return board

def drop_piece():
    pass

def is_valid_location(board, column):
    if column > 6 or column <= 0:
        invalid = True
    
def get_next_open_row():
    pass    

board_create(columns, row)

while not game_over:
    if turn == 0:
        while invalid == True:
            column = input("Player 1 make your selection (1-6):")
            is_valid_location(board, column, invalid)
    else:
        while invalid == True:
            column = input("Player 2 make your selection (1-6):")
            is_valid_location(board, column, invalid)
    turn = turn + 1
    turn = turn % 2

Would appreciate some help.