def triangles():    def Cao(m, n):        num = den = 1        order = [x + 1 for x in range(n)]        inver = [n - x for x in range(n)]        for i in range(m):            num = num * inver[i]            den = den * order[i]        return int(num / den)    n = 0    while True:        L = []        for i in range(n+1):            L.append(Cao(i,n))        yield(L)        n = n+1

根据杨辉三角定义来写的，没有发挥生成器的优点。