python应用-给出行数，输出相应的杨辉三角

def main():
    num = int(input('Number of rows: '))
    yh = [[]] * num
    for row in range(num):
        yh[row] = [None] * (row + 1)
        for col in range(row+1):
            if col == 0 or col == row:
                yh[row][col] = 1
            else:
                yh[row][col] = yh[row - 1][col] + yh[row - 1][col - 1]
            print(yh[row][col], end='\t')
        print()

if __name__ == '__main__':
    main()
结果：
Number of rows: 5
1
1   1
1   2   1
1   3   3   1
1   4   6   4   1