def leap_year(year):
if year % 400 == 0:
return True
if year % 100 == 0:
return False
if year % 4 == 0:
return True
return False
def days_in_month(month, year):
if month in {1, 3, 5, 7, 8, 10, 12}:
return 31
if month == 2:
if leap_year(year):
return 29
return 28
return 30
print(days_in_month(2, 2016)) # 29