how to delete json object using python?

Question

I am using python to delete and update a JSON file generated from the data provided by user, so that only few items should be stored in the database. I want to delete a particular object from the JSON file.

My JSON file is:

[
  {
      "ename": "mark",
      "url": "Lennon.com"
  },
  {
      "ename": "egg",
      "url": "Lennon.com"
  }
]

I want to delete the JSON object with ename mark.

As I am new to python I tried to delete it by converting objects into dict but it is not working. Is there any other way to do it? i tried this one:

index=0
while index < len(data):
    next=index+1
    if(data[index]['ename']==data[next]['ename']):
        print "match found at"
        print "line %d and %d" %(next,next+1)
        del data[next]
    index +=1

Answer 1

Here's a complete example that loads the JSON file, removes the target object, and then outputs the updated JSON object to file.

#!/usr/bin/python                                                               

# Load the JSON module and use it to load your JSON file.                       
# I'm assuming that the JSON file contains a list of objects.                   
import json
obj  = json.load(open("file.json"))

# Iterate through the objects in the JSON and pop (remove)                      
# the obj once we find it.                                                      
for i in xrange(len(obj)):
    if obj[i]["ename"] == "mark":
        obj.pop(i)
        break

# Output the updated file with pretty JSON                                      
open("updated-file.json", "w").write(
    json.dumps(obj, sort_keys=True, indent=4, separators=(',', ': '))
)

The main point is that we find the object by iterating through the objects in the loaded list, and then pop the object off the list once we find it. If you need to remove more than one object in the list, then you should store the indices of the objects you want to remove, and then remove them all at once after you've reached the end of the for loop (you don't want to modify the list while you iterate through it).

Answer 2

The proper way to json is to deserialize it, modify the created objects, and then, if needed, serialize them back to json. To do so, use the json module. In short, use <deserialized object> = json.loads(<some json string>) for reading json and <json output> = json.dumps(<your object>) to create json strings. In your example this would be:

import json
o = json.loads("""[
    {
        "ename": "mark",
        "url": "Lennon.com"
    },
    {
        "ename": "egg",
        "url": "Lennon.com"
    }
]""")
# kick out the unwanted item from the list
o = filter(lambda x: x['ename']!="mark", o)
output_string = json.dumps(o)

Answer 3

Your json file contains in a list of objects, which are dictionaries in Python. Just replace the list with a new one that doesn't have the object in it:

import json

with open('testdata.json', 'rb') as fp:
    jsondata = json.load(fp)

jsondata = [obj for obj in jsondata if obj['ename'] != 'mark']

print(json.dumps(jsondata, indent=4))

Answer 4

You have a list there with two items, which happen to be dictionaries. To remove the first, you can use list.remove(item) or list.pop(0) or del list[0].

http://docs.python.org/2/tutorial/datastructures.html#more-on-lists

Answer 5

You need to use the json module. I'm assuming python2. Try this:

import json
json_data = json.loads('<json_string>')

for i in xrange(len(json_data)):
  if(json_data[i]["id"] == "mark"):
    del json_data[i]
    break