python时间输出

请问大家，我已经到这一步了，但是怎么按题目要求来把不足两位的前面补零讷？？

print("{:02d}:{:02d}:{:02d}".format(a,b,c))

m = int(input())
a = m // 3600
b = m % 3600 // 60
c = m % 3600 % 60
if a < 10:
a = "0" + str(a)
if b < 10:
b = "0" + str(b)
if c < 10:
c = "0" + str(c)

print(a, ":", b, ":", c)

seconds =eval(input())
m, s = divmod(seconds, 60)
h, m = divmod(m, 60)
print("%02d:%02d:%02d" % (h, m, s))