clock converter

import regex, sys

### Script that turns 24 hr clock string into 12 hr clock string with AM/PM ###

time = sys.argv[1]
pattern = "(\d{1,2}):(\d{1,2})"

#~~~~~~~~~~~~~~~~~~~#

#Error check no.1
try:
  result = list(regex.findall(pattern, time)[0])

  #Error check no.2 (nested!)
  if len(result) != 2:
    print("Input cannot be parsed. Please format like this: `##:##`.")
    sys.exit(-1)
except:
  print("Input cannot be parsed. Please format like this: `##:##`.")
  sys.exit(-1)

result = [int(i) for i in result]

#~~~~~~~~~~~~~~~~~~~#

#Failure detection system (Error check no.3)
failureReasons = {
  "Hours too high.":   (result[0] > 23),
  "Minutes too high.": (result[1] > 59)
}
Failures = [i for i in failureReasons if failureReasons[i]]
if Failures:

  #Lists any errors like this:
  #     [!] Reason 1
  #     [!] Reason 2
  print("Unable to run because of the following:\n{}".format("\n".join(["\t[!] " + i for i in Failures])))
  sys.exit(-1)

#~~~~~~~~~~~~~~~~~~~#

def main():
  if result[0] > 12:
    result[0] -= 12
    result.append("PM")
  else:
    result.append("AM")

  #Formats `result` array into a string
  #Prepends "0" to `m` if it doesn't have one, so that it appears as "2:04" for example, instead of "2:4".
  timeformatter = lambda h, m ,suf: "{}:{} {}".format(h, "0"+str(m) if len(str(m)) == 1 else m, suf)

  print("Time (12hr): {output}".format(output=timeformatter(*result)))

#~~~~~~~~~~~~~~~~~~~#

if __name__ == '__main__':
  main()