age_in_days.py

# This is my solution to the programming problen posted as part of
# Udacity's Intro to Programming Nanodegree.

# Original problem statement:
# Given your birthday and the current date, calculate your age
# in days. Compensate for leap days. Assume that the birthday
# and current date are correct dates.
# Simply put, if you were born 1 Jan 2012 and todays date is
# 2 Jan 2012 you are 1 day old.

daysOfMonths = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]

def isLeapYear(year):
    ##
    # Your code here. Return True or False
    # Pseudo code for this algorithm is found at
    # http://en.wikipedia.org/wiki/Leap_year#Algorithm
    ##
    if not year % 4 == 0:
        return False
    elif not year % 100 == 0:
        return True
    elif not year % 400 == 0:
        return False

    return True


def daysBetweenDates(y1, m1, d1, y2, m2, d2):
    ##
    # Your code here.
    ##
    days = 0
    #  scenario: same years
    if y2 - y1 == 0:
        #  scenario: same years, same months
        if m2 - m1 == 0:
            days = d2 - d1
        #  scenario: same years, different months
        else:
            month = m1
            while month <= m2:
                days += (daysOfMonths[month - 1])
                month += 1

            # Now rationalise 'days' to deduct extra days added from
            # month of birth as well as the current year
            days = days - d1 - (daysOfMonths[m2 - 1] - d2)
            if isLeapYear(y1):
                days += 1

    #  scenario: different years
    else:
        days = 0
        year = y1
        month = m1
        while year <= y2:
            while month <= 12:
                if isLeapYear(year) and month == 2:
                    days += (daysOfMonths[month - 1] + 1)
                else:
                    days += daysOfMonths[month - 1]
                month += 1
                if year == y2 and month > m2:
                    break
            year += 1
            month = 1

        # Now rationalise 'days' to deduct extra days added from
        # month of birth as well as the current year
        days -= d1
        if isLeapYear(year) and m2 == 2:
            days -= (daysOfMonths[m2 - 1] + 1 - d2)
        else:
            days -= (daysOfMonths[m2 - 1] - d2)

    return days

print(daysBetweenDates(1912, 12, 12, 2012, 12, 12))
# same year same month
print(daysBetweenDates(2017, 1, 1, 2017, 1, 15))
print(daysBetweenDates(2017, 1, 1, 2017, 1, 2))
print(daysBetweenDates(2012, 12, 7, 2012, 12, 7))
# same year different months
print(daysBetweenDates(2017, 1, 1, 2017, 2, 15))
# different years
print(daysBetweenDates(1980, 10, 15, 2017, 2, 7))
print(daysBetweenDates(2012, 6, 29, 2013, 6, 29))