def triangles():
    n=1
    L=[1]
    while True:
        yield L
        L=[1] + [L[i]+L[i+1] for i in range(len(L)-1)] + [1]
        n+=1


n=0
for t in triangles():
    print(t)
    n=n+1
    if n==10:
        break

yield 相当中断的return吧