"Time Conversion" Python implementation

Question

Problem Statement

You are given time in AM/PM format. Convert this into a 24 hour format.

Note Midnight is \$ 12:00:00AM \$ or \$ 00:00:00 \$ and 12 Noon is \$ 12:00:00PM. \$

Input Format

Input consists of time in the AM/PM format i.e. hh:mm:ssAM or hh:mm:ssPM where \$ 01 \le hh \le 12 \$, \$ 00 \le mm \le 59 \$, \$ 00 \le ss \le 59 \$

Output Format

You need to print the time in 24 hour format i.e. hh:mm:ss where

\$ 00 \le hh \le 23 \$, \$ 00 \le mm \le 59 \$, \$ 00 \le ss \le 59 \$

Sample Input

\$ 07:05:45PM \$

Sample Output

\$ 19:05:45 \$

Solution

class AbsTime(object):

    def __init__(self, hh, mm=0, ss=0, pm=False):
        self.hh = hh
        self.mm = mm
        self.ss = ss
        self.pm = pm

    def add(self, time):
        self.hh += time.hh
        self.mm += time.mm
        self.ss += time.ss

        if self.ss >= 60:
            self.ss -= 1
            self.mm += 1
        if self.mm >= 60:
            self.mm -= 1
            self.hh = self.hh % 24
        return self

    def midnight(self):
        return not self.pm and str(self) in ['00:00:00', '12:00:00']

    def noon(self):
        return self.pm and str(self) == '12:00:00'

    def __str__(self):
        return "{0:02d}:{1:02d}:{2:02d}".format(self.hh, self.mm, self.ss)

    def get(self):
        if self.midnight():
            return AbsTime(0)
        if self.noon():
            return AbsTime(12)
        if self.pm:
            if self.hh == 12:
                hh = self.hh
            else:
                hh = self.hh + 12
            return AbsTime(hh, self.mm, self.ss)
        else:
            return AbsTime(self.hh % 12, self.mm, self.ss)

    @classmethod
    def create_from_string(cls, time):
        pm = True if time[-2:] == 'PM' else False      
        hh, mm, ss = map(int, time[:-2].split(':'))
        return cls(hh, mm, ss, pm)


def main(time):
    if time == '00:00:00':
        return time

    abstime = AbsTime.create_from_string(time)
    return abstime.get()


if __name__ == '__main__':
    TIME = raw_input().strip()
    print main(TIME)
    #print main('00:00:00')   #00:00:00
    #print main('12:00:00PM') #12:00:00
    #print main('12:00:00AM') #00:00:00
    #print main('02:00:00PM') #14:00:00
    #print main('02:00:00AM') #02:00:00 
    #print main('11:59:00AM') #11:59:00
    #print main('12:59:00PM') #12:59:00
    #print main('01:00:00PM') #13:00:00
    #print main('11:59:59PM') #23:59:59
    #print main('12:59:59AM') #00:59:59

It really took me a while to do this simple solution, its fast when we do just structural programming but once I thought to step into OOP world things really got confusing. How can I improve this design?

Answer 1

Using an internal representation of time that is as simple as possible would simplify your work. For example, using internally seconds since midnight, the add method could become

def add(self, other):
    self.seconds = (self.seconds + other.seconds) % SECONDS_IN_DAY

Answer 2

You could just use strptime and strftime from the time module to do this:

current_time = time.strptime(time_string, "%I:%M:%S%p")
time_formatted = time.strftime("%H:%M:%S", current_time)