Converting 12-hour time to 24-hour time

# https://www.codewars.com/kata/59b0a6da44a4b7080300008a

def to24hourtime(hour, minute, period):
    if period == "am" and hour == 12:
        hour = 0
    elif period == "pm" and hour != 12:
        hour += 12
    hour = str(hour).rjust(2,"0")
    minute = str(minute).rjust(2,"0")
    return hour + minute