How to merge two json string in Python?

Question

I recently started working with Python and I am trying to concatenate one of my JSON String with existing JSON String. I am also working with Zookeeper so I get the existing json string from zookeeper node as I am using Python kazoo library.

# gets the data from zookeeper
data, stat = zk.get(some_znode_path)
jsonStringA = data.decode("utf-8")

if I print jsonStringA it gives me like this -

{"error_1395946244342":"valueA","error_1395952003":"valueB"}

But if I do print json.loads(jsonString) then it prints out like this -

{u'error_1395946244342': u'valueA', u'error_1395952003': u'valueB'}

Here jsonStringA will have my existing JSON String. Now I have another key-value pair which I need to add in the exiting jsonStringA -

Below is my Python code -

# gets the data from zookeeper
data, stat = zk.get(some_znode_path)
jsonStringA = data.decode("utf-8")

timestamp_in_ms = "error_"+str(int(round(time.time() * 1000)))
node = "/pp/tf/test/v1"
a,b,c,d = node.split("/")[1:]
host_info = "h1"
local_dc = "dc3"
step = "step2"

My existing jsonStringA will be like this after extracting from zookeeper -

{"error_1395946244342":"valueA","error_1395952003":"valueB"}

Now I need to append this key-value pair in the jsonStringA -

"timestamp_in_ms":"Error Occured on machine "+host_info+" in datacenter "+ local_dc +" on the "+ step +" of process "+ c +"

So in short I need to merge below key-value pair -

"error_1395952167":"Error Occured on machine h1 in datacenter dc3 on the step2 of process test"

So final JSON String will look like this -

{"error_1395946244342":"valueA","error_1395952003":"valueB","error_1395952167":"Error Occured on machine h1 in datacenter dc3 on the step2 of process test"}

Is this possible to do?

Answer 1

Assuming a and b are the dictionaries you want to merge:

c = {key: value for (key, value) in (a.items() + b.items())}

To convert your string to python dictionary you use the following:

import json
my_dict = json.loads(json_str)

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Update: full code using strings:

# test cases for jsonStringA and jsonStringB according to your data input
jsonStringA = '{"error_1395946244342":"valueA","error_1395952003":"valueB"}'
jsonStringB = '{"error_%d":"Error Occured on machine %s in datacenter %s on the %s of process %s"}' % (timestamp_number, host_info, local_dc, step, c)

# now we have two json STRINGS
import json
dictA = json.loads(jsonStringA)
dictB = json.loads(jsonStringB)

merged_dict = {key: value for (key, value) in (dictA.items() + dictB.items())}

# string dump of the merged dict
jsonString_merged = json.dumps(merged_dict)

But I have to say that in general what you are trying to do is not the best practice. Please read a bit on python dictionaries.

---

Alternative solution:

jsonStringA = get_my_value_as_string_from_somewhere()
errors_dict = json.loads(jsonStringA)

new_error_str = "Error Ocurred in datacenter %s blah for step %s blah" % (datacenter, step)
new_error_key = "error_%d" % (timestamp_number)

errors_dict[new_error_key] = new_error_str

# and if I want to export it somewhere I use the following
write_my_dict_to_a_file_as_string(json.dumps(errors_dict))

And actually you can avoid all these if you just use an array to hold all your errors.