Donald Donald - 9 days ago 5
JSON Question

Extract values from JSON in Python

This is a reply from the Google Distance Matrix. I would like to have only the two value's as an output and I'm trying to extract it with Python.

{
"destination_addresses" : [ "Hoorn, Nederland" ],
"origin_addresses" : [ "Amsterdam, Nederland" ],
"rows" : [
{
"elements" : [
{
"distance" : {
"text" : "45,0 km",
"value" : 44952
},
"duration" : {
"text" : "40 min.",
"value" : 2423
},
"status" : "OK"
}
]
}
],
"status" : "OK"
}


This is what I've tried so far. I want to have a reply from Google every 15 minutes and write it to a file. But in the file I only want the value for distance and duration and I have no luck in achieving that. I'm not sure if the reply from Google is proper JSON so I've tried json.loads but it did not allow me to extract certain parts from the reply. Any ideas?

import requests
import json
import datetime
from apscheduler.schedulers.blocking import BlockingScheduler

uri = "https://maps.googleapis.com/maps/api/distancematrix/json?origins=Amsterdam&destinations=Hoorn&mode=driving&key="
now = datetime.datetime.now()

def job():
datum = now.strftime("%Y-%m-%d %H:%M")
print datum
text_file = open('tijdsduur.txt', 'a')
batch = requests.get(uri)
data = batch.text
jdata = json.loads(data)
print jdata['elements']['distance']['value']
text_file.write(data)
text_file.write('\n')
text_file.close()

job()
scheduler = BlockingScheduler()
scheduler.add_job(job, 'interval', minutes=15)
scheduler.start()


Error when I try json.loads: KeyError 'elements'

Answer

json.loads will take a string paramater. Cast the value you receive from google to a string.

import json
a="""{
   "destination_addresses" : [ "Hoorn, Nederland" ],
   "origin_addresses" : [ "Amsterdam, Nederland" ],
   "rows" : [
      {
         "elements" : [
            {
               "distance" : {
                  "text" : "45,0 km",
                  "value" : 44952
               },
               "duration" : {
                  "text" : "40 min.",
                  "value" : 2423
               },
               "status" : "OK"
            }
         ]
      }
   ],
   "status" : "OK"
}"""

b = json.loads(a)
dist,dur = b['rows'][0]['elements'][0]['distance'], b['rows'][0]['elements'][0]['duration']
print dist
print dur

Output:

{u'text': u'40 min.', u'value': 2423}
{u'text': u'45,0 km', u'value': 44952}
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