calling a method inside a class-Python

Question

class Time:

    def __init__(self,x,y,z):
        self.hour=x
        self.minute=y
        self.second=z

    def __str__(self):
        return "({:02d}:{:02d}:{:02d})".format(self.hour, self.minute, self.second)

    def time_to_int(time):
        minutes=time.hour*60+time.minute
        seconds=minutes*60+time.second
        return seconds

    def int_to_time(seconds):
        time=Time()
        minutes,time.second=divmod(seconds,60)
        time.hour,time.minute=divmod(minutes,60)
        return time

    def add_time(t1,t2):
        seconds=time_to_int(t1)+time_to_int(t2)
        return int_to_time(seconds)

start=Time(9,45,00)
running=Time(1,35,00)
done=add_time(start,running)
print(done)

I am new to python and i've been doing some practice lately.I came across a question and i've written the code for the same.But I am repeatedly getting an error: "add_time is not defined". I tried defining a main() method but then it doesn't print anything.Please help.

Answer 1

You haven't created an object to the above class.

Any function/method inside a class can only be accessed by an object of that class .For more information on the fundamentals of Object Oriented Programming, please check this page.

Meanwhile for this to work, define your class in the following way :

class Time:

def __init__(self,x=None,y=None,z=None):
    self.hour=x
    self.minute=y
    self.second=z

def __str__(self):
    return "({:02d}:{:02d}:{:02d})".format(self.hour, self.minute, self.second)

def time_to_int(time):
    minutes=time.hour*60+time.minute
    seconds=minutes*60+time.second
    return seconds

def int_to_time(seconds):
    time=Time()
    minutes,time.second=divmod(seconds,60)
    time.hour,time.minute=divmod(minutes,60)
    return time

def add_time(t1,t2):
    seconds=time_to_int(t1)+time_to_int(t2)
    return int_to_time(seconds)

and outside the class block, write the following lines :

TimeObject = Time()
start=Time(9,45,00)
running=Time(1,35,00)
TimeObject.add_time(start,running)
print "done"

I however suggest you to write the add_time function outside the class because you are passing the objects to the class as the parameters to the function within the same class and it is considered as a bad design in object oriented programming. Hope it helps. Cheers!

Answer 2

This works fine for me as long as you specified 3 args in your constructor

def int_to_time(seconds):
    time=Time(0,0,0) # just set your 3 positionals args here
    minutes,time.second=divmod(seconds,60)
    time.hour,time.minute=divmod(minutes,60)
    return time

Another way to avoid it could be:

class Time:
    def __init__(self,x=0,y=0,z=0):
        self.hour=x
        self.minute=y
        self.second=z

If you want to add your functions to your class (such as time_to_int, int_to_time or even add_time) then you will need to indent with one more level of 4 spaces and add self to your method parameters