Python - having trouble selecting single value from json data

Question

I have the following code from which I want to select a singular piece of data from the JSON.

    j = {
    "data": [
        {
            "astronomicalDawn": "2023-01-16T04:58:21+00:00",
            "astronomicalDusk": "2023-01-16T17:00:31+00:00",
            "civilDawn": "2023-01-16T06:38:18+00:00",
            "civilDusk": "2023-01-16T15:20:34+00:00",
            "moonFraction": 0.36248449454701365,
            "moonPhase": {
                "closest": {
                    "text": "Third quarter",
                    "time": "2023-01-14T22:34:00+00:00",
                    "value": 0.75
                },
                "current": {
                    "text": "Waning crescent",
                    "time": "2023-01-16T06:00:00+00:00",
                    "value": 0.7943440617174506
                }
            },
            "moonrise": "2023-01-16T01:01:55+00:00",
            "moonset": "2023-01-16T09:53:57+00:00",
            "nauticalDawn": "2023-01-16T05:46:36+00:00",
            "nauticalDusk": "2023-01-16T16:12:16+00:00",
            "sunrise": "2023-01-16T07:28:07+00:00",
            "sunset": "2023-01-16T14:30:45+00:00",
            "time": "2023-01-16T06:00:00+00:00"
        },
        {
            "astronomicalDawn": "2023-01-17T04:57:26+00:00",
            "astronomicalDusk": "2023-01-17T17:02:07+00:00",
            "civilDawn": "2023-01-17T06:37:07+00:00",
            "civilDusk": "2023-01-17T15:22:26+00:00",
            "moonFraction": 0.26001046334874545,
            "moonPhase": {
                "closest": {
                    "text": "Third quarter",
                    "time": "2023-01-14T21:31:00+00:00",
                    "value": 0.75
                },
                "current": {
                    "text": "Waning crescent",
                    "time": "2023-01-17T06:00:00+00:00",
                    "value": 0.8296778757434323
                }
            },
            "moonrise": "2023-01-17T02:38:30+00:00",
            "moonset": "2023-01-17T10:01:03+00:00",
            "nauticalDawn": "2023-01-17T05:45:35+00:00",
            "nauticalDusk": "2023-01-17T16:13:58+00:00",
            "sunrise": "2023-01-17T07:26:40+00:00",
            "sunset": "2023-01-17T14:32:54+00:00",
            "time": "2023-01-17T06:00:00+00:00"
        }
    ],
    "meta": {
        "cost": 1,
        "dailyQuota": 10,
        "lat": 58.7984,
        "lng": 17.8081,
        "requestCount": 1,
        "start": "2023-01-16 06:00"
    }
}

print(j['data']['moonPhase'])

Which gives me this error;

TypeError: list indices must be integers or slices, not str

That error is in regard to the very last line of the code. But changing the very very last line to print(j['data']) works.

What am I doing wrong - I am trying to select moonPhase data. It turns me on. Thank you.

Zach Flanders · Accepted Answer · 2023-01-17 04:00:37Z

1

Try:

print(j['data'][0]['moonPhase'])

or

print(j['data'][1]['moonPhase'])

Explanation: The data property of the json object contains a list. There are two items in the list (item 0 and item 1). You must first select an item using [0] or [1] before selecting the moonPhase property of one of the objects in the list.

edit: If you want to select only items where the moonPhase is in the future try:

print([
    item['moonPhase']
    for item in j['data']
    if (
        datetime.fromisoformat(
            item['moonPhase']['current']['time']
        ).timestamp() > 
        datetime.now().timestamp()
    )
])

output

[{'closest': {'text': 'Third quarter', 'time': '2023-01-14T21:31:00+00:00', 'value': 0.75}, 'current': {'text': 'Waning crescent', 'time': '2023-01-17T06:00:00+00:00', 'value': 0.8296778757434323}}]

edited Jan 17, 2023 at 4:00

answered Jan 17, 2023 at 3:46

Zach Flanders

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3 Comments

uncrayon Over a year ago

Works. Why? This also works j['data'][0]['moonPhase']['current']).

uncrayon Over a year ago

I see - there is two results. One for 1.16 and one for 1.17, Starts at astronomicaldawn. So i should do a for loop to make it dynamic / do work for each item. Thanks. I'll accept you answer, but I think a for loop is best. Thanks again.

Zach Flanders Over a year ago

Thanks, I added an example of using a list comprehension to compare the moonPhase datetimes against the current datetime.

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