[FIXED] How can I extract a single value from a JSON response?

Issue

I wrote some code to get data from a web API. I was able to parse the JSON data from the API, but the result I gets looks quite complex. Here is one example:

>>> my_json
{'name': 'ns1:timeSeriesResponseType', 'declaredType': 'org.cuahsi.waterml.TimeSeriesResponseType', 'scope': 'javax.xml.bind.JAXBElement$GlobalScope', 'value': {'queryInfo': {'creationTime': 1349724919000, 'queryURL': 'http://waterservices.usgs.gov/nwis/iv/', 'criteria': {'locationParam': '[ALL:103232434]', 'variableParam': '[00060, 00065]'}, 'note': [{'value': '[ALL:103232434]', 'title': 'filter:sites'}, {'value': '[mode=LATEST, modifiedSince=null]', 'title': 'filter:timeRange'}, {'value': 'sdas01', 'title': 'server'}]}}, 'nil': False, 'globalScope': True, 'typeSubstituted': False}

Looking through this data, I can see the specific data I want: the 1349724919000 value that is labelled as 'creationTime'.

How can I write code that directly gets this value?

I don't need any searching logic to find this value. I can see what I need when I look at the response; I just need to know how to translate that into specific code to extract the specific value, in a hard-coded way. I read some tutorials, so I understand that I need to use [] to access elements of the nested lists and dictionaries; but I can't figure out exactly how it works for a complex case.

More generally, how can I figure out what the "path" is to the data, and write the code for it?

Solution

For reference, let's see what the original JSON would look like, with pretty formatting:

>>> print(json.dumps(my_json, indent=4))
{
    "name": "ns1:timeSeriesResponseType",
    "declaredType": "org.cuahsi.waterml.TimeSeriesResponseType",
    "scope": "javax.xml.bind.JAXBElement$GlobalScope",
    "value": {
        "queryInfo": {
            "creationTime": 1349724919000,
            "queryURL": "http://waterservices.usgs.gov/nwis/iv/",
            "criteria": {
                "locationParam": "[ALL:103232434]",
                "variableParam": "[00060, 00065]"
            },
            "note": [
                {
                    "value": "[ALL:103232434]",
                    "title": "filter:sites"
                },
                {
                    "value": "[mode=LATEST, modifiedSince=null]",
                    "title": "filter:timeRange"
                },
                {
                    "value": "sdas01",
                    "title": "server"
                }
            ]
        }
    },
    "nil": false,
    "globalScope": true,
    "typeSubstituted": false
}

That lets us see the structure of the data more clearly.

In the specific case, first we want to look at the corresponding value under the 'value' key in our parsed data. That is another dict; we can access the value of its 'queryInfo' key in the same way, and similarly the 'creationTime' from there.

To get the desired value, we simply put those accesses one after another:

my_json['value']['queryInfo']['creationTime'] # 1349724919000

Answered By - dm03514

Answer Checked By - Katrina (PHPFixing Volunteer)