Python 中的 Try/Except：如何避免重复？

Question

我有一个类，可以将 API 引发的低级异常转换为高级异常。该类充满了复杂、重复的错误处理逻辑。我正在寻找减少这种重复的Pythonic 方法。

这是一个人为的例子。

class ApiWrapperException(Exception):
  pass

class ApiWrapper(object):

  def __init__(self, api):
    self._api = api

  def do_one_thing(self):
    print 'do_one_thing stuff before API call'
    try:
      self._api.do_one_thing()
    except ApiException:
      print 'ApiWrapper caught an ApiException. Doing complicated error handling logic. Raising a different exception.'
      raise ApiWrapperException
    print 'do_one_thing stuff after API call'

  def do_another_thing(self):
    print 'do_another_thing stuff before API call'
    try:
      self._api.do_another_thing()
    except ApiException:
      print 'ApiWrapper caught an ApiException. Doing complicated error handling logic. Raising a different exception.'
      raise ApiWrapperException
    print 'do_another_thing stuff after API call'

在此示例中，该类ApiWrapper将低级转换ApiException为更好的ApiWrapperException. 但有很多重复。

选项 1：使用函数包装器

我可以将重复的代码放入内部函数中，如下所示：

def handle_api_errors(api_callable):
  def call(*args, **kwargs):
    try:
      return api_callable(*args, **kwargs)
    except ApiException:
      print 'ApiWrapper caught an ApiException. Doing complicated error handling logic. Raising a different exception.'
      raise ApiWrapperException
  return call

该类ApiWrapper简化为：

class ApiWrapper(object):

  def __init__(self, api):
    self._api = api

  def do_one_thing(self):
    print 'do_one_thing stuff before API call'
    handle_api_errors(self._api.do_one_thing)()
    print 'do_one_thing stuff after API call'

  def do_another_thing(self):
    print 'do_another_thing stuff before API call'
    handle_api_errors(self._api.do_another_thing)()
    print 'do_another_thing stuff after API call'

选项 2：使用上下文管理器

我可以将重复的代码放入上下文管理器中，如下所示：

@contextlib.contextmanager
def handle_api_errors():
  try:
    yield
  except ApiException:
    print 'ApiWrapper caught an ApiException. Doing complicated error handling logic. Raising a different exception.'
    raise ApiWrapperException

该类ApiWrapper简化为：

class ApiWrapper(object):

  def __init__(self, api):
    self._api = api

  def do_one_thing(self):
    print 'do_one_thing stuff before API call'
    with handle_api_errors():
      self._api.do_one_thing()
    print 'do_one_thing stuff after API call'

  def do_another_thing(self):
    print 'do_another_thing stuff before API call'
    with handle_api_errors():
      self._api.do_another_thing()
    print 'do_another_thing stuff after API call'

选项 3：使用装饰器（按照 @ZachGates 的建议）

我可以将重复的代码放入装饰器中，如下所示：

def handle_api_errors(api_calling_func):
  def decorated_func(*args, **kwargs):
    try:
      api_calling_func(*args, **kwargs)
    except ApiException:
      print 'ApiWrapper caught an ApiException. Doing complicated error handling logic. Raising a different exception.'
      raise ApiWrapperException
  return decorated_func

该类ApiWrapper简化为：

class ApiWrapper(object):

  def __init__(self, api):
    self._api = api

  @handle_api_errors
  def do_one_thing(self):
    print 'do_one_thing stuff before API call'
    self._api.do_one_thing()
    print 'do_one_thing stuff after API call'

  @handle_api_errors
  def do_another_thing(self):
    print 'do_another_thing stuff before API call'
    self._api.do_another_thing()
    print 'do_another_thing stuff after API call'

哪个选项被认为是最Pythonic的？有更好的选择吗？

Answer 1

那这个呢 ？

class ApiWrapper(object):

    def __init__(self, api):
        self._api = api

    def api_call(self, methodname, *args, **kwargs):
        method = getattr(self._api, methodname)
        try:
            return method(*args, **kwargs)
        except ApiException:
            print 'ApiWrapper caught an ApiException. Doing complicated error handling logic. Raising a different exception.'
            raise ApiWrapperException

    def do_one_thing(self):
        print 'do_one_thing stuff before API call'
        self.api_call("do_one_thing")
        print 'do_one_thing stuff after API call'