python

def timeConversion(s):

len_s = len(s)      
if len_s !=10:
    return None
am_or_pm = str(s)[len_s-2]
time_24 = str(s)[:-2]
hour = int(str(s)[:2])

if am_or_pm == 'P' and  hour!=12:
    time_24 = str(hour + 12 )+str(s)[2:-2]
else:
    if am_or_pm == 'A' and hour ==12:
        time_24 = "00"+str(s)[2:-2]

return time_24