杨辉三角——python

a = []
for i in range(8):
    a.append([])
    for j in range(8):
        a[i].append(0)
for i in range(8):
    a[i][0] = 1
    a[i][i] = 1
for i in range(2,8):
    for j in range(1,i):
        a[i][j] = a[i-1][j-1] + a[i-1][j]
for i in range(8):
    for j in range(i+1):
        print("{:3d}".format(a[i][j]),end=" ")
    print()