helo,

I learn Classes and methods according to a manual "Think Python: How to Think Like a Computer Scientist"

I am stuck on "Polymorphism" There is a part using built-in function sum.

I don't know what to do... It should be connected to __add__ function, but still the code must be somhow changed. If I use just total=t1+t2+t3 it works.

Here is a link to a web manual:

http://www.greenteapress.com/thinkpython/html/book018.html#toc189

total=sum([t1,t2,t3])

here is a code:

```
def int_to_time(seconds):
time = Time()
minutes, time.second = divmod(seconds, 60)
time.hour, time.minute = divmod(minutes, 60)
return time
class Time(object):
def __init__(self, hour=0, minute=0, second=0):
self.hour = hour
self.minute = minute
self.second = second
def __add__(self, other):
seconds = self.time_to_int() + other.time_to_int()
return int_to_time(seconds)
def time_to_int(self):
minutes = self.hour * 60 + self.minute
seconds = minutes * 60 + self.second
print seconds
return seconds
def __str__(self):
return '%.2d:%.2d:%.2d' % (self.hour, self.minute, self.second)
def main():
t1 = Time(7, 43)
t2 = Time(7, 41)
t3 = Time(7, 37)
total = sum([t1, t2, t3])
print total
if __name__ == '__main__':
main()
```

I really approciate your help guys. Many thanks!