python - Python 中的尝试/异常(exception) : appropriate for parsing dictionaries?

Question

我正在尝试解析包含嵌套列表和字典的字典。我试图检测给定的键是否存在并将其值保存到适当的变量中。下面的代码可以工作，但感觉非常困惑。有没有正确/更好的方法来处理这个问题？

def wit_response(self, message_text=None):
    if message_text is not None:
        resp = self.client.message(message_text)
        print(resp)

        try:
            intent = resp['entities']['intent'][0]['value']
        except:
            intent = None
        try:
            location = resp['entities']['location'][0]['value']
        except:
            location = None
        try:
            datetimefrom = resp['entities']['datetime'][0]['values'][0]['from']['value']
        except:
            datetimefrom = None
        try:
            datetimeto = resp['entities']['datetime'][0]['values'][0]['to']['value']
        except:
            datetimeto = None

resp 的示例。

{u'entities': {u'intent': [{u'confidence': 0.99699357488585, u'value': u'weather'}], u'location': [{u'suggested': True, u'confidence': 0.87101, u'type': u'value', u'value': u'like'}]}, u'msg_id': u'0jkzwqMkSkpZsKJYx', u'_text': u'What is the weather like?'}

Answer 1

如果不使用某种辅助函数或新容器，您将无法变得更短。一种方法是编写一个函数:

def try_get(obj, key):
    if not key:
        return obj

    key, _, rest = key.partition('.')

    try:
        key = int(key)
    except ValueError:
        pass

    try:
        return try_get(obj[key], rest)
    except (KeyError, IndexError):
        return None

像这样使用它:

intent = try_get(resp, 'entities.intent.0.value')
location = try_get(resp, 'entities.location.0.value')
datetimefrom = try_get(resp, 'entities.datetime.0.values.0.from.value')
datetimeto = try_get(resp, 'entities.datetime.0.values.0.to.value')

JSON 不允许整数字典键，因此这应该明确允许您遍历从 JSON 解析的任何对象。