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    • yield的使用。执行到yield，中断，生成数，下次又继续执行
    • 每次在最后增加0，便于生成下一行
    1. # 打印杨辉三角
    2. def print_list(array):
    3.     for ele in array:
    4.         print(ele, end=' ')
    5.     print('')
    7. def triangle():
    8.     N = [1]
    9.     while True:
    10.         yield N
    11.         N.append(0) # 用于后续叠加
    12.         N = [N[i]+N[i-1] for i in range(len(N))]
    14. def print_triangle(x):
    15.     count = 0
    16.     for t in triangle():
    17.         print_list(t)
    18.         count += 1
    19.         if count == x:
    20.             break
    21. print_triangle(int(input()))