Parsing json with python3

Question

Newbie python programmer here, I have the following json response:

[
  {
    "type": "Incursion",
    "state": "mobilizing",
    "influence": 1,
    "has_boss": true,
    "faction_id": 500019,
    "constellation_id": 20000739,
    "staging_solar_system_id": 30005054,
    "infested_solar_systems": [
      30005050,
      30005051,
      30005052,
      30005053,
      30005054,
      30005055
    ]
  },
  {
    "type": "Incursion",
    "state": "established",
    "influence": 0,
    "has_boss": false,
    "faction_id": 500019,
    "constellation_id": 20000035,
    "staging_solar_system_id": 30000248,
    "infested_solar_systems": [
      30000244,
      30000245,
      30000246,
      30000247,
      30000248,
      30000249,
      30000250,
      30000251,
      30000252,
      30000253
    ]
  },
  {
    "type": "Incursion",
    "state": "mobilizing",
    "influence": 0,
    "has_boss": false,
    "faction_id": 500019,
    "constellation_id": 20000161,
    "staging_solar_system_id": 30001101,
    "infested_solar_systems": [
      30001097,
      30001098,
      30001099,
      30001100,
      30001101,
      30001102
    ]
  },
  {
    "type": "Incursion",
    "state": "established",
    "influence": 0,
    "has_boss": false,
    "faction_id": 500019,
    "constellation_id": 20000647,
    "staging_solar_system_id": 30004434,
    "infested_solar_systems": [
      30004425,
      30004426,
      30004427,
      30004428,
      30004429,
      30004430,
      30004431,
      30004432,
      30004433,
      30004434,
      30004435
    ]
  },
  {
    "type": "Incursion",
    "state": "established",
    "influence": 0.061500001698732376,
    "has_boss": false,
    "faction_id": 500019,
    "constellation_id": 20000570,
    "staging_solar_system_id": 30003910,
    "infested_solar_systems": [
      30003904,
      30003906,
      30003908,
      30003909,
      30003910,
      30003903
    ]
  }
]

The original code was written to parse an XML reponse.

This is the code in question:

incursion_constellations = []

if (online):
    inc = urllib2.urlopen('https://esi.tech.ccp.is/latest/incursions/')
else:
    inc = file(r'incursions.json', 'r')

jinc = json.load(inc)

for j in jinc['items']:
    incursion_constellations.append(str(j['constellation']['id_str']))


for s in all_stations:
    cur.execute("SELECT constellationID FROM mapSolarSystems WHERE solarSystemID = " + str(s['ssid']))
    res = cur.fetchone()
    cid = str(res[0])
    s['incursion'] = cid in incursion_constellations

The area I have having a hard time understanding is this: for j in jinc['items']:

I am getting this error:

Traceback (most recent call last):
  File "./stations.py", line 201, in <module>
    for j in jinc['items']:
TypeError: list indices must be integers, not str

Can anyone help me understand how to convert this into being able to parse the json response and retrieve the constellation_id and append it to a list?

Thanks in advance.

@IgnacioVazquez-Abrams - I don't. The original code was reading and parsing an XML reponse, and the developer of the API changed it to a json response. — Steven Sheeley
– Steven Sheeley, Commented Aug 1, 2017 at 19:25
@JaredGoguen Those were from the original XML reponse the api returned. — Steven Sheeley
– Steven Sheeley, Commented Aug 1, 2017 at 19:25

Laser · Accepted Answer · 2017-08-01 19:32:07Z

2

Change your original loop to:

for j in jinc:
    incursion_constellations.append(str(j['constellation_id']))

But you need to be sure that constellation_id in json is the same id that was under ['constellation']['id_str'] previously

answered Aug 1, 2017 at 19:32

Laser

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1 Comment

Steven Sheeley Over a year ago

That did it, thank you very much. I have a better understanding of what was needed to do now.

weichichi · Accepted Answer · 2017-08-01 19:35:23Z

1

Seeing the [ and ] at the beginning and the end of the response, it seems like this json response is list, not a dict, just as your error is suggesting.

If it is a list, you should be using integer as index, instead of str, like you'd do in dict. Hence, your code should be something like

jinc[0]['constellation_id']

(I don't see where the ['constellation']['id_str'] part comes from)

whatever goes inside the [ and ] is in a list, and should be using an integer index. the ones in { and } are in dict, and should use str index.

to loop through it, just use range and len.

a similar question has been answered here.

edited Aug 1, 2017 at 19:35

answered Aug 1, 2017 at 19:24

weichichi

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2 Comments

Steven Sheeley Over a year ago

The 'item' was from the original XML response. I am trying, unsuccessfully, to convert this code to python, in which I have never written before, I am a PHP programmer.

Charles Duffy Over a year ago

This isn't in any way a Python-specific issue: even in PHP, you can't access a member of a list using a non-numeric string as the index. So the application logic is clearly not matching here -- maybe you're iterating over list elements in the PHP but dropped that from the Python?

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