Time Duration in python - python-3.x

Question

Given two strings :
ex:
start_time="3:00 PM"
Duration="3:10"
Start time is in 12-hour clock format (ending in AM or PM), and duration time
that indicates the number of hours and minutes
Assume that the start times are valid times.The minutes in the duration time will
be a whole number less than 60, but the hour can be any whole number.
I need to add the duration time to the start time and return the result
(WITHOUT ANY USE OF LIBRARIES).
The result should be in 12-hour clock format (ending in AM or PM) indicates the
number of hours and minutes
ex:
start_time = "6:30 PM"
Duration = "205:12"
# Returns: 7:42 AM
I Tried and finally got the required answer but unable to produce correct AM or PM for
the result after addition.
what I Tried:
start_time = "6:30 PM"
Duration = "205:12"
#My answer =7:42
#expected :7:42 AM
Can someone help me with the logic to produce correct AM or PM after addition of start
time and Duration.
def add_time(a,b):
a=a.split()
b=b.split()
be=int(a[0][:a[0].find(':')])
af=int(a[0][a[0].find(':')+1:])
be1 = int(b[0][:b[0].find(':')])
af1 = int(b[0][b[0].find(':') + 1:])
return(((be+be1)//24)+1)
s=be+(be1)%12
p=af+af1
if ((s>12) and (p<60)) :
return(str(s-12)+":"+str(p))
elif ((s<12) and (p>60)) :
f = p-60
if len(str(f))<=1:
return(str(s+1)+":"+str('0'+str(f)))
else:
return (str(s + 1)+":"+(str(f)))
elif ((s<12) and (p<60)) :
return(str(s)+":"+str(p))
elif ((s>12) and (p>60)):
f=p-60
if len(str(f)) <= 1:
return (str((s -12)+1)+":"+('0' + str(f)))
else:
return (str((s -12)+1)+":"+(str(f)))
print(add_time("10:10 PM", "3:30"))
# Returns: 1:40 AM
print(add_time("11:43 PM", "24:20"))
# Returns: 12:03 AM

Answer 1

Your code does not seem to cover all edge cases, e.g. add_time("11:43 PM", "1:20") returns None because the case s==12 is not covered.
Therefore one should put <= instead of < in the respective if conditions. The case where the addition of the minutes leads to hours greater than 12 although the addition of the hours itself did not, is not covered either. So we should check the minutes first and the hours after that instead of simultaneously.
To make the code more readable, we use f-strings and can use str.split() with an argument, forgive me for changing the code quite a bit:
def add_time(a,b):
start = a.split()
start_h, start_m = [int(val) for val in start[0].split(':')]
start_app = start[1]
dur_h, dur_m = [int(val) for val in b.split(':')]
end_m = start_m+dur_m
end_h = end_m//60
end_m %= 60
end_h += start_h+dur_h
if (end_h//12)%2==0:
end_app = start_app
else:
end_app = 'AM' if start_app=='PM' else 'PM'
return f'{end_h:02}:{end_m:02} {end_app}'