python上下文管理器异常问题解决方法

class File:
 def __enter__(self):
  return file_obj
 def __exit__(self, exc_type, exc_value, exc_tb):
  # with 退出时释放文件资源
  file_obj.close()
  # 如果 with 内有异常发生 抛出异常
  if exc_type is not None:
   raise exception

class File(object):
 def __init__(self, file_name, method):
  self.file_obj = open(file_name, method)
 def __enter__(self):
  return self.file_obj
 def __exit__(self, type, value, traceback):
  print("Exception has been handled")
  self.file_obj.close()
  return True
 
with File('demo.txt', 'w') as opened_file:
 opened_file.undefined_function()
 
# Output: Exception has been handled