python - How to parse data in JSON format?

316
votes

My project is currently receiving a JSON message in python which I need to get bits of information out of. For the purposes of this, let's set it to some simple JSON in a string:

jsonStr = '{"one" : "1", "two" : "2", "three" : "3"}'

So far I've been generating JSON requests using a list and then json.dumps, but to do the opposite of this I think I need to use json.loads. However I haven't had much luck with it. Could anyone provide me a snippet that would return "2" with the input of "two" in the above example?

5
pythonjsonparsing
Note: For those that come here with data that uses ' single-quote string delimiters, you may have accidentally created string representations for Python dictionaries instead. JSON will always use " delimiters. If so, repair your code that produces that output to use json.dumps() instead of str() or repr(), and head over to Convert a String representation of a Dictionary to a dictionary? to figure out how to recover your Python data. Other clues you have a Python literal? Look for None, True or False, JSON would use null, true & false. - Martijn Pieters♦
Those who do not have a jsonStr but a list of dictionaries (possibly with ' single-quote string delimiters), also have a look here: stackoverflow.com/questions/41168558/… - questionto42

5 Answers

547
votes

Very simple:

import json
data = json.loads('{"one" : "1", "two" : "2", "three" : "3"}')
print data['two']
92
votes

Sometimes your json is not a string. For example if you are getting a json from a url like this:

j = urllib2.urlopen('http://site.com/data.json')

you will need to use json.load, not json.loads:

j_obj = json.load(j)

(it is easy to forget: the 's' is for 'string')

61
votes

For URL or file, use json.load(). For string with .json content, use json.loads().

#! /usr/bin/python

import json
# from pprint import pprint

json_file = 'my_cube.json'
cube = '1'

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

# pprint(data)

print "Dimension: ", data['cubes'][cube]['dim']
print "Measures:  ", data['cubes'][cube]['meas']
31
votes

Following is simple example that may help you:

json_string = """
{
    "pk": 1, 
    "fa": "cc.ee", 
    "fb": {
        "fc": "", 
        "fd_id": "12345"
    }
}"""

import json
data = json.loads(json_string)
if data["fa"] == "cc.ee":
    data["fb"]["new_key"] = "cc.ee was present!"

print json.dumps(data)

The output for the above code will be:

{"pk": 1, "fb": {"new_key": "cc.ee was present!", "fd_id": "12345", 
 "fc": ""}, "fa": "cc.ee"}

Note that you can set the ident argument of dump to print it like so (for example,when using print json.dumps(data , indent=4)):

{
    "pk": 1, 
    "fb": {
        "new_key": "cc.ee was present!", 
        "fd_id": "12345", 
        "fc": ""
    }, 
    "fa": "cc.ee"
}
-1
votes

Can use either json or ast python modules:

Using json :
=============

import json
jsonStr = '{"one" : "1", "two" : "2", "three" : "3"}'
json_data = json.loads(jsonStr)
print(f"json_data: {json_data}")
print(f"json_data['two']: {json_data['two']}")

Output:
json_data: {'one': '1', 'two': '2', 'three': '3'}
json_data['two']: 2




Using ast:
==========

import ast
jsonStr = '{"one" : "1", "two" : "2", "three" : "3"}'
json_dict = ast.literal_eval(jsonStr)
print(f"json_dict: {json_dict}")
print(f"json_dict['two']: {json_dict['two']}")

Output:
json_dict: {'one': '1', 'two': '2', 'three': '3'}
json_dict['two']: 2