Getting values from Json data in Python

Question

I have a json file that I am trying to pull specific attribute data from. The Json data is essentially a dictionary. Before the data is turned into a file, it is first held in a variable like this:

params = {'f': 'json', 'where': '1=1', 'geometryType': 'esriGeometryPolygon', 'spatialRel': 'esriSpatialRelIntersects','outFields': '*', 'returnGeometry': 'true'}
r = requests.get('https://hazards.fema.gov/gis/nfhl/rest/services/CSLF/Prelim_CSLF/MapServer/3/query', params)

cslfJson = r.json()

and then written into a file like this:

path = r"C:/Workspace/Sandbox/ScratchTests/cslf.json"
with open(path, 'w') as f:
    json.dump(cslfJson, f, indent=2)

within this json data is an attribute called DFIRM_ID. I want to create an empty list called dfirm_id = [], get all of the values for DFIRM_ID and for that value, append it to the list like this dfirm_id.append(value). I am thinking I need to somehow read through the json variable data or the actual file, but I am not sure how to do it. Any suggestions on an easy method to accomplish this?

dfirm_id = []
for k, v in cslf:
    if cslf[k] == 'DFIRM_ID':
        dfirm.append(cslf[v])

As requested, here is what print(cslfJson) looks like: It actually prints a huge dictionary that looks like this:

{'displayFieldName': 'CSLF_ID', 'fieldAliases': {'OBJECTID': 'OBJECTID', 'CSLF_ID': 'CSLF_ID', 'Area_SF': 'Area_SF', 'Pre_Zone': 'Pre_Zone', 'Pre_ZoneST': 'Pre_ZoneST', 'PRE_SRCCIT': 'PRE_SRCCIT', 'NEW_ZONE': 'NEW_ZONE', 'NEW_ZONEST': .... {'attributes': {'OBJECTID': 26, 'CSLF_ID': '13245C_26', 'Area_SF': 5.855231804165408e-05, 'Pre_Zone': 'X', 'Pre_ZoneST': '0.2 PCT ANNUAL CHANCE FLOOD HAZARD', 'PRE_SRCCIT': '13245C_STUDY1', 'NEW_ZONE': 'A', 'NEW_ZONEST': None, 'NEW_SRCCIT': '13245C_STUDY2', 'CHHACHG': 'None (Zero)', 'SFHACHG': 'Increase', 'FLDWYCHG': 'None (Zero)', 'NONSFHACHG': 'Decrease', 'STRUCTURES': None, 'POPULATION': None, 'HUC8_CODE': None, 'CASE_NO': None, 'VERSION_ID': '2.3.3.3', 'SOURCE_CIT': '13245C_STUDY2', 'CID': '13245C', 'Pre_BFE': -9999, 'Pre_BFE_LEN_UNIT': None, 'New_BFE': -9999, 'New_BFE_LEN_UNIT': None, 'BFECHG': 'False', 'ZONECHG': 'True', 'ZONESTCHG': 'True', 'DFIRM_ID': '13245C', 'SHAPE_Length': 0.009178426056888393, 'SHAPE_Area': 4.711699932249018e-07, 'UID': 'f0125a91-2331-4318-9a50-d77d042a48c3'}}, {'attributes': .....}

Well, sadly you've truncated the most important bit, i.e. 'NEW_ZONEST': .... {'attributes': {'OBJECTID': We need to know the structure of your dictionary, e.g. is 'attributes' dictionary a value of 'NEW_ZONEST or something else? Basically, it would help if you gave us an example dictionary we can run. — jpp
– jpp, Commented Aug 21, 2018 at 17:08

Alex · Accepted Answer · 2018-08-21 17:47:07Z

1

If your json data is already a dictionary, then take advantage of that. The beauty of a dictionary / hashmap is that it provides an average time complexity of O(1).

Based on your comment, I believe this will solve your problem:

dfirm_id = []
for feature in cslf['features']:
    dfirm_id.append(feature['attributes']['DFIRM_ID'])

edited Aug 21, 2018 at 17:47

answered Aug 21, 2018 at 16:55

Alex

13516 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

gwydion93 Over a year ago

They are all nested like this { displayFieldName: "CSLF_ID", ..., features` : [ {attributes: {..., DFIRM: "13245C", ...}, ...} ] `

Collectives™ on Stack Overflow

Getting values from Json data in Python

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related