pythonpandasjson-normalize

How to create pandas dataframe from nested json with dictionary


I'm trying to create a pandas dataframe form json file. I've seen a multiple solutions to this problem which uses built in functions from_dict/json_normalize yet I'm unable to apply it to my code. Here's how my data is structured in json file:

     "data": [
   {
      "groups": {
         "data": [
               {
               "group": "Math",
               "year_joined": "2009"
               },
               {
               "group_name": "History",
               "year_joined": "2011"
               },
               {
               "group_name": "Biology",
               "year_joined": "2010"
               }
         ]
      },
      "id": "12512"
   },

When I'm trying to normalize this data with pandas function like this:

path = 'mypath'
f = open(path)
data = json.load(f)

test = pd.json_normalize(
            data['data'], 
            errors='ignore') 

I just receive something like this:

    id      groups.data
0   12512   [{'group_name': 'Math', 'year_joined': '2009', 'gr...
1   23172   [{'group_name': 'Chemistry', 'year_joined': '2005'...

I want this data to look like this (solution 1):

    id      group     year_joined
0   12512   group1    year1
1   12512   group2    year2
2   12512   group3    year3

Or like this (solution 2):

    id      group                   year_joined
0   12512   group1,group2,group3    year1,year2,year3
1   23172   group4,group5           year4,year5

How can i achieve it? I tried passing 'record_path' parameter to 'json_normalize' function but it doesn't change anything. I tried to use 'DataFrame.from_dict' function to work around this but I failed. The only way I was able to get to solution 1 was to just create multiple loops that iterated through everything in json file and add it to separate list. It kinda works but takes a lot of time on bigger datasets.

How could i use built-in pandas tools to process files which are nested as dictionaries in 3rd layer of the file as presented above?


Solution

  • You need to collect the information from the data dictionary

    solution 1

    d = {}
    for group in data["data"]:
        groups = [x["group_name"] for x in group['groups']["data"]]
        d['id'] = d.get('id', []) + [group['id']] * len(groups)
        d['group'] = d.get('group', []) + groups
        d['year_joined'] = d.get('year_joined', []) + [x["year_joined"] for x in group['groups']["data"]]
    
    df = pd.DataFrame(d)
    

    Output

          id      group year_joined
    0  12512       Math        2009
    1  12512    History        2011
    2  12512    Biology        2010
    3  23172  Chemistry        2007
    4  23172  Economics        2008
    

    solution 2

    d = {}
    for group in data["data"]:
        d['id'] = d.get('id', []) + [group['id']]
        d['group'] = d.get('group', []) + [','.join(x["group_name"] for x in group['groups']["data"])]
        d['year_joined'] = d.get('year_joined', []) + [','.join(x["year_joined"] for x in group['groups']["data"])]
    
    df = pd.DataFrame(d)
    

    Output

          id                 group     year_joined
    0  12512  Math,History,Biology  2009,2011,2010
    1  23172   Chemistry,Economics       2007,2008