func_leap_year_month.py

# Number of days per month. First value placeholder for indexing purposes.
month_days = [0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]

def is_leap(year):
    """Return True for leap years, False for non-leap years. """
    """ this sign is called doc-string, this explains twhat the function is supposed to do"""

    return year % 4 == 0 and (year % 100 != 0 or year % 400 == 0)

def days_in_month(year, month):
    """" Return number if the days in that month in that year.  """

    if not 1 <= month <= 12:
        return 'Invalid Month'

    if month == 2 and is_leap(year):
        return 29

    return month_days[month]

print(is_leap(2017))
print(days_in_month(2020, 2))