[Tutor] Is this correct?

[Alan Gauld]

>> Personally I prefer to put the initialisation
>> into an  __init__() method, 

> Thanks for your comments. Please, see below a new
> version of that exercise. What do you think?

> hour = int( raw_input('Enter the hour: ') )
> min = int( raw_input('Enter the minute: ') )
> sec = int( raw_input('Enter the sec: ') )
> 
> 
> class Time:
> def __init__(self, hours = 0, minutes = 0, seconds =
> 0):
> self.hours = hours
> self.minutes = minutes
> self.seconds = seconds
> 
> def printTime(self):  # By convention, the first
> parameter of a method is called self.
> '''printTime:
> 
> Prints the time.'''
> print str(self.hours) + ":" + str(self.minutes) +
> ":" + str(self.seconds)
> 
> 
> def convertToSeconds(t):
> ''' convertToSeconds:
> 
> Converts a Time object into an integer.'''
> minutes = t.hours * 60 + t.minutes
> seconds = t.minutes * 60 + t.seconds
> return seconds

So far so good.

> def makeTime(seconds):
> ''' makeTime:
> Converts from an integer to a Time object.'''

> time = Time()
> time.hours = seconds/3600
> seconds = seconds - time.hours * 3600
> time.minutes = seconds/60
> seconds = seconds - time.minutes * 60
> time.seconds = seconds
> return time

I'd rework this bit to:

hours = seconds/3600
seconds = seconds  % 3600  # use % to get remainder
minutes = seconds/60
seconds = seconds  % 60 #and again
time = Time(hours,minutes,seconds)
return time

And by using divmod() you can combine two lines into one:

hours,seconds = divmod(seconds,3600)
minutes,seconds = divmod(seconds,60)
time = Time(hours,minutes,seconds)
return time

> def addTime(t1, t2):
> ''' addTime function:
> 
> Calculates the sum of two times.'''
> seconds = convertToSeconds(t1) + convertToSeconds(t2)
> return makeTime(seconds)

> currentTime = Time()
> currentTime.hours = hour
> currentTime.minutes = min
> currentTime.seconds = sec
> currentTime.printTime()

I'd move the raw_input lines from the top to here so 
that the logical connection between them and this is clearer.
And you don't use your init method here. Do this instead:

currentTime = Time(hour,min,sec)
currentTime.printTime()

One of the principles of OOP is that you should try not to access 
the data members of the class directly, use methods to do all the work.
[The reason for this is that we can overrride the methods in 
subclasses but we can't override the data so using data directly 
limits the effectiveness of subclassing as a mechanism, for changing 
the behaviour of your code without modifying it. (In Computer Science 
speak this is known as the Open/Closed principle - open for extension, 
closed for modification) ]

HTH,

Alan G
Author of the learn to program web tutor
http://www.freenetpages.co.uk/hp/alan.gauld