python3，打印一年的某一天是一年的第几天

year = int(input('year:'))
month = int(input('month:'))
day = int(input('day:'))

months = (0,31,59,90,120,151,181,212,243,273,304,334)

if (0<month<12):
    sum = months[month-1]
else:
    print('input error')

sum +=day
leap =0

if (year % 400 == 0) or ((year % 4 == 0) and (year % 100 != 0)):
    leap ==1;
if (leap == 1) and (month > 2):
    sum += 1
print('it is the %dth day.' % sum)