Python JSON解析，检查值是否以某些内容开头

Question

I am reading in JSON from a URL and am running into some issues manipulating the data.

JSON is as follows:

{
  "Id": "1234,
  "something": "{..."
}

I read in the JSON from a url as follows, which works fine.

response = urllib.urlopen(url)
data = json.loads(response.read())

Now what I want to do is whenever the value of "something" starts with '{', append "Id" to a list. Here is what I have:

for x in data:
    if x.get("something").startswith('{'):
        do something...

I get the following error:

if x.get("something").startswith('{'):  

AttributeError: 'NoneType' object has no attribute 'startswith'

Anyway I can get this to work, or other suggestions on how to accomplish this?

Answer 1

You are on the right track..

First you need to check that "something" exists, otherwise your code will turn "None" which is why you are getting an error, you could try the following to ensure that this is the case:

for key, value in data.items():
    if key == "something":
        if value.startswith('{'):
            # do something...

Answer 2

I think you only need this part :

if data.get("something").startswith("{"):

because its a dict , you can get the dict value by calling the key with the dict name. No need to loop.

While you looping it will loop through the keys.If you want to do it in your way you can do like this :

for x, y in data.items():
    if x=="something" and y.startswith("{"):
          do what you want...

Answer 3

good_items = ["""something""" for k in data if k.startswith('{')]

Instead of """something""", you could put a method call to a function taking a single argument (the individual key). This will yield a list of items from data for which the condition matches. Hope that helps...

Answer 4

data is a dictionary, and "something" is a key in the dictionary that is or is not present. The following code checks if the key is present (then it extracts the value associated with the code, and checks if the value starts with a "{"); or not (then it replaces the value with an empty string that does not start with a "{"):

if data.get("something","").startswith("{"): ...

If the key is definitely present, the solution is even simpler:

if data["something"].startswith("{"): ...