How to find a particular json value by key?

Question

There is a json like this:

{
  \"P1\": \"ss\",
  \"Id\": 1234,
  \"P2\": {
      \"P1\": \"cccc\"
  },
  \"P3\": [
      {
          \"P1\": \"aaa\"
      }
         


        

Answer 1

I don't think there's any way of finding all values associated with P1 without iterating over the whole structure. Here's a recursive way to do it that first deserializes the json object in a file into an equivalent Python object. To simplify things most of the work is done via a private nested function.

def find_values(id, obj):
    results = []

    def _find_values(id, obj):
        try:
            for key, value in obj.iteritems():
                if key == id:
                    results.append(value)
                elif not isinstance(value, basestring):
                    _find_values(id, value)
        except AttributeError:
            pass

        try:
            for item in obj:
                if not isinstance(item, basestring):
                    _find_values(id, item)
        except TypeError:
            pass

    if not isinstance(obj, basestring):
        _find_values(id, obj)
    return results

import json

with open('data.json') as json_file:
    obj = json.load(json_file)

print find_values('P1', obj)

Answer 2

Using json to convert the json to Python objects and then going through recursively works best. This example does include going through lists.

import json
def get_all(myjson, key):
    if type(myjson) == str:
        myjson = json.loads(myjson)
    if type(myjson) is dict:
        for jsonkey in myjson:
            if type(myjson[jsonkey]) in (list, dict):
                get_all(myjson[jsonkey], key)
            elif jsonkey == key:
                print myjson[jsonkey]
    elif type(myjson) is list:
        for item in myjson:
            if type(item) in (list, dict):
                get_all(item, key)