example.py

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

def number_of_days_between_months(m1, m2):
  days = 0
  for month in range(m1, m2):
    days += daysOfMonths[month]
  return days

def days_alive(y1, m1, d1, y2, m2, d2):
  
  days = 0

  if y2 - y1 == 1:
    if m2 > m1:
      days += daysOfMonths[m1] - d1
      days = days + number_of_days_between_months(m1, m2 - 1)
      days = days + d2

      if m1 >= 2:
        days = days + 1
    else:
      days = d2 - d1
  else:
    for year in range(y1, y2 + 1):
      # the first year may be an incomplete year
      if y1 == year:
        # calculate days left in month born
        days += daysOfMonths[m1] - d1
        
        # calculate days for each complete month for the rest of the year
        days = days + number_of_days_between_months(m1, 11)

        # account for a leap year
        if is_leap_year(year) && m1 <= 2:
          days = days + 1

      # the last year is also incomplete
      elif y1 == y2:
        # calculate days lived in month, which is basically just adding d2
        days = days + d2

        # calculate days for each complete month for the year
        days = days + number_of_days_between_months(0, m2 - 1)

        # account for leap year
        if is_leap_year(year) and m2 >= 2:
          days = days + 1

      # any years in between are completely lived
      else:
        for month in daysOfMonths:
          days = days + daysOfMonths[month]

        if is_leap_year(year):
          days = days + 1

  return days