python NameError: name 'xxx' is not define

问题:

puzzle = [[' 1', ' 2', ' 3', ' 4'], [' 5', ' 6', ' 7', ' 8'],[ ' 9', '10', '11', '12'], ['13', '14', '15', ' X']]

def find_pos(alist, item):
    for i in alist:
        for j in range(4):
            if i[j] == item:
                row = alist.index(i)
                col = j

find_pos(puzzle,' X')

a = row
print(a)

I think I defined the name row by running the function find_pos, if not, how to fix it to get row

Do not put any print in the find_pos function

回答1:

Just return the values from the function:

puzzle = [[' 1', ' 2', ' 3', ' 4'], [' 5', ' 6', ' 7', ' 8'],[ ' 9', '10', '11', '12'], ['13', '14', '15', ' X']]

def find_pos(alist, item):
    for i in alist:
        for j in range(4):
            if i[j] == item:
                row = alist.index(i)
                col = j
                return row, col

row, col = find_pos(puzzle,' X')

print(row)

Note that if the item isn't found, it will return None (because every function that doesn't return anything returns None by default), in which case the code will throw an error.