Use the json module to produce JSON output:

import json

with open(outputfilename, 'wb') as outfile:
    json.dump(row, outfile)

This writes the JSON result directly to the file (replacing any previous content if the file already existed).

If you need the JSON result string in Python itself, use json.dumps() (added s, for 'string'):

json_string = json.dumps(row)

The L is just Python syntax for a long integer value; the json library knows how to handle those values, no L will be written.

Demo string output:

>>> import json
>>> row = [1L,[0.1,0.2],[[1234L,1],[134L,2]]]
>>> json.dumps(row)
'[1, [0.1, 0.2], [[1234, 1], [134, 2]]]'

You can achieve this by using built-in json module

import json

arrayJson = json.dumps([{"email": item} for item in pyList])

import json

array = '{"fruits": ["apple", "banana", "orange"]}'
data  = json.loads(array)
print(data['fruits']) 
# the print displays:
# ['apple', 'banana', 'orange']

You had everything you needed. data will be a dict, and data['fruits'] will be a list

Just adding onto alexce's response, you can easily convert the restructured data into JSON:

import json
json.dumps(result)

There are some potential security concerns with top-level arrays. I'm not sure if they're still valid with modern browsers, but you may want to consider wrapping it in an object.

import json
json.dumps({'results': result})

When you receive multiple JSON objects, those are in the form of a list (so between []). You could:

1. covert JSON string to python dictionary using json.loads()
2. filter using the dict
3. dump dictionary into a JSON string using json.dumps()

input = """[
    {"document": 
        {"id": "1","image": "https://xxx.xxx.png","name": "xxx"}},
    {"document":
        {"id": "2","image": "https://xx2.xxx.png","name": "xx2"}}
    ]"""
input_dic = json.loads(input)
tmp = []
for item in input_dic:
    tmp.append(json.dumps(item["document"]))
output = json.dumps(tmp)
print(output)

Hope I got your question.

Instead of creation of separate dictionaries and then merging them, try to create the final (joined) dictionary, without any intermediate step.

The fragment of your code creating concepts list is OK.

Then add import json at the start of your program, and at the end, add the following code:

res = []    # Result
for row in concepts:
    curr = res    # Current object
    for str in row:
        if len(curr) == 0:
            curr.append({})
        curr = curr[0]
        if str not in curr:
            curr[str] = []
        curr = curr[str]

print(json.dumps(res, indent=2))

As you can see, the idea is:

1. The result (res) is a list contaning a single dictionary object.
2. Processing of each row causes "going down the object tree", on each string - element of the current row.
3. Initially added value to a dictionary (for some key) contains an empty list. If there is no "more embedded" element, this ends this "path".
4. Before "going down the tree" the program adds an empty dictionary to this list, if it has not beed added earlier.
5. The last step is to add an empty array, under the key equal to the current string.

The printed result (slightly reformatted to take less rows) is:

[{"machine learning": [{
    "inear model": [{
      "linear regression": [{
        "least squares": []}]}],
    "neural network": [{
      "neuron model": [{
        "activation function": []}]}],
    "multi-layer network": [{
      "perceptron": [{
        "connection right": []}]}],
    "reinforcement learning": [{
      "model learning": [{
        "strategy evaluation": [],
        "strategy improvement": []}],
      "model-free learning": [{
        "monte carlo method": [],
        "time series learning": []}]}],
    "imitate learning": [{
      "directly imitate learning": [{
        "inverse reinforcement learning": []}]}]
    }]
}]

decode JSON strings into dicts and put them in a list, last, convert the list to JSON

json_list = []
json_list.append(json.loads(JSON_STRING))
json.dumps(json_list)

or more pythonic syntax

output_list = json.dumps([json.loads(JSON_STRING) for JSON_STRING in JSON_STRING_LIST])