How can I convert JSON to CSV?

Question

I have a JSON file I want to convert to a CSV file. How can I do this with Python?

I tried:

import json
import c         


        

Answer 1

I am assuming that your JSON file will decode into a list of dictionaries. First we need a function which will flatten the JSON objects:

def flattenjson( b, delim ):
    val = {}
    for i in b.keys():
        if isinstance( b[i], dict ):
            get = flattenjson( b[i], delim )
            for j in get.keys():
                val[ i + delim + j ] = get[j]
        else:
            val[i] = b[i]

    return val

The result of running this snippet on your JSON object:

flattenjson( {
    "pk": 22, 
    "model": "auth.permission", 
    "fields": {
      "codename": "add_message", 
      "name": "Can add message", 
      "content_type": 8
    }
  }, "__" )

is

{
    "pk": 22, 
    "model": "auth.permission', 
    "fields__codename": "add_message", 
    "fields__name": "Can add message", 
    "fields__content_type": 8
}

After applying this function to each dict in the input array of JSON objects:

input = map( lambda x: flattenjson( x, "__" ), input )

and finding the relevant column names:

columns = [ x for row in input for x in row.keys() ]
columns = list( set( columns ) )

it's not hard to run this through the csv module:

with open( fname, 'wb' ) as out_file:
    csv_w = csv.writer( out_file )
    csv_w.writerow( columns )

    for i_r in input:
        csv_w.writerow( map( lambda x: i_r.get( x, "" ), columns ) )

I hope this helps!