clock.py

class clock(object):
	def __init__(self, hours, minutes, seconds):

		self.set_clock(hours, minutes, seconds)

	def set_clock(self,hours, minutes, seconds):

		if type(hours) == int and 0 <= hours and hours < 24:
			self._hours = hours
		else:
			raise TypeError("Hours have to be an integer between 0 and 23")

		if type(minutes) == int and 0 <= minutes and minutes < 60:
			self._minutes = minutes
		else:
			raise TypeError("Minutes have to be an integer between 0 and 59")


		if type(seconds) == int and 0 <= minutes and minutes < 60:
			self._seconds = seconds
		else:
			raise TypeError("Seconds have to be an integer between 0 and 59")

	def __str__(self):

		
#02d formats an integer (d) to a field of minimum width 2 (2), with zero-padding on the left (leading 0):


		return "{0:02d}:{1:02d}:{2:02d}".format(self._hours,self._minutes,self._seconds)

	def tick(self):

		if self._seconds == 59:
			self._seconds = 0
			if self._minutes == 59:
				self._minutes = 0
				if self._hours == 23:
					self._hours = 0
				else:
					self._hours += 1
			else:
				self._minutes += 1
		else:
			self._seconds += 1

if __name__ == '__main__':
	x = clock(23,59,59)
	print(x)
	x.tick()
	print(x)
	y = str(x)
	print(type(y))