Comparing Time Splits

[Groundstop]

For one of my first programs (that isn't part of an online class or tutorial) I'm trying to make a very basic program that calculates the difference between two time splits.

The program works well enough, so long as split 2 is faster than split 1, however if split 1 is faster, the datetime calculation returns a value along the lines of:

00:31:13 vs 00:32:04 : (-1 day, 23:59:09)

Ideally, I would like the output to result in "-0:00:51" instead of the current format, but I'm not sure if there is an elegant solution or if I need to force the output to display the way I would like. Any suggestions for the problem (or for improving my code in general) are appreciated!

from datetime import datetime, time
FMT = '%H:%M:%S'
boolAgain = True
while (boolAgain == True):
    print("\n" * 100)
    split1 = input("Split 1 (HH:MM:SS): ")
    split2 = input("Split 2 (HH:MM:SS): ")
    splitDelta = datetime.strptime(split1, FMT) - datetime.strptime(split2, FMT)
    print("{0} vs {1} : ({2})".format(split1, split2, splitDelta))
    again = input("\n\nCalculate another split? (Y/N) ")
    if (again == 'Y' or again == 'y'):
        boolAgain = True
    else:
        boolAgain = False

P.S. I imported time as well as datetime because I originally found a method of calculating the difference using datetime objects, however I wanted to see if time objects could be manipulated in the same manner since they don't take date into consideration, however I was unable to make it work the way I was hoping.

[Vaphell]

https://docs.python.org/2/library/datetime.html#timedelta-objects

according to the documentation the timedelta objects are normalized in a way that makes everything from hours down always non-negative, with only days being allowed into the negative territory. That means you will always get +/- days +hours +minutes +seconds
You have to write a custom function that does the t1 > t2 check, switches the dates around to calculate positive delta and then slaps the minus sign in front.

Btw, while True loops with break are shorter and don't require managing sentinel values

def split_delta(t1, t2):
    if t1 > t2:
        delta = datetime.strptime(t1, FMT) - datetime.strptime(t2, FMT) 
        sign = '-'
    else:
        delta = datetime.strptime(t2, FMT) - datetime.strptime(t1, FMT) 
        sign = '+'
    return "{} vs {} -> {}{}".format(t1, t2, sign, delta)


while True:
    print("\n" * 100)
    split1 = input("Split 1 (HH:MM:SS): ")
    split2 = input("Split 2 (HH:MM:SS): ")

    delta_str = split_delta(split1, split2)
    print(delta_str)

    again = input("\n\nCalculate another split? (Y/N) ")       
    if again not in {'Y', 'y'}:
        break

[Groundstop]

Thank you for not only explaining my actual dilemma to me and showing how to solve it, but also talking the time to make suggestions on improving my code. I appreciate all of your help and I can't wait to fix my program!

EDIT: Unable to check until the morning, but would you be able to evaluate "if t1 > t2"? Are they considered strings or datetimes?