Pythonの非常に便利な2つのデコレーターを解説

import signal,functools #The following two libraries will be used 
class TimeoutError(Exception): pass #Define an Exception to be thrown after a timeout 
def timeout(seconds, error_message = 'Function call timed out'):
  def decorated(func):
    def _handle_timeout(signum, frame):
      raise TimeoutError(error_message)
    def wrapper(*args, **kwargs):
      signal.signal(signal.SIGALRM, _handle_timeout)
      signal.alarm(seconds)
      try:
        result = func(*args, **kwargs)
      finally:
        signal.alarm(0)
      return result
    return functools.wraps(func)(wrapper)
  return decorated

@timeout(5) #Finalize the following slowfunc function to force a TimeoutError Exception if it does not return within 5s 
def slowfunc(sleep_time):
  import time
  time.sleep(sleep_time) # this function is to sleep sleep_time seconds 
slowfunc(3) #sleep 3 seconds, normal return no exceptions
slowfunc(10) #is terminated 

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import sys,os,linecache
def trace(f):
  def globaltrace(frame, why, arg):
    if why == "call": return localtrace
    return None
  def localtrace(frame, why, arg):
    if why == "line":
      # record the file name and line number of every trace
      filename = frame.f_code.co_filename
      lineno = frame.f_lineno
      bname = os.path.basename(filename)
      print("{}({}): {}".format( bname,
        lineno,
        linecache.getline(filename, lineno).strip('\r\n')),)
    return localtrace
  def _f(*args, **kwds):
    sys.settrace(globaltrace)
    result = f(*args, **kwds)
    sys.settrace(None)
    return result
  return _f

@trace
def xxx():
  print (1)
  print (22)
  print (333)
xxx() # call