无法到达 python 3.8 中的嵌套 JSON

Question

Working with a response from a Websockets subscription.

The response reads like this:

{'jsonrpc': '2.0', 'method': 'subscription', 'params': {'channel': 'book.BTC-PERPETUAL.none.1.100ms', 'data': {'timestamp': 1588975154127, 'instrument_name': 'BTC-PERPETUAL', 'change_id': 19078703948, 'bids': [[10019.5, 8530.0]], 'asks': [[10020.0, 506290.0]]}}}

And I'm trying to reach the first and only values inside "bids" and "asks" arrays via json.loads()

Code looks like this:

   async def __async__get_ticks(self):
  async with self.ws as echo:
     await echo.send(json.dumps(self.request))
     while True:
            response = await echo.receive()
            responseJson = json.loads(response)
            print(responseJson["params"]["data"])

And error says:

 print(responseJson["params"]["data"])

KeyError: 'params'

However I try, it doesn't want to catch any of the JSON after "jsonprc" , for which it successfully returns 2.0 . Anything beyond that always comes up with an error.

I tried using .get() , and it helps to go one level deeper, but still not more.

Any ideas on how to format this properly and reach the bids and asks ?

Thank you in advance.

Answer 1

I would suggest using the dict.get() method, but make sure that you set it to return an empty dictionary when querying dictionaries that are expected to have nested dicts.

By default (if you don't specify a second argument to dict.get() ), it will return None . This explains why you were only able to go one level deep.

Here's an example:

empty_dict = {}
two_level_dict = {
    "one": {
        "level": "deeper!"
    }
}

# This will return None and the second get call will not fail, because
# the first get returned an empty dict for the .get("level") call to succeed. 
first_get = empty_dict.get("one", {}).get("level")

# This will return 'deeper!'
second_get = two_level_dict.get("one", {}).get("level")

print(first_get)
print(second_get)