As ZdaR's post illustrates, to create a json, you need to build the corresponding Python data structure (lists for json arrays, dictionaries for json objects) and serialize it at the end. So the question is almost the same as how to create a list in a loop, because after creating the list, what remains is serialization which is as simple as json.loads(data).

The task in the OP can be done in two loops:

data = [{'Title': line.getText(strip=True)} for line in games_html.findAll('a')]

for i, line in enumerate(games_html.findAll('div', class_="product_score")):
    data[i]['Score'] = line.getText(strip=True)

# serialize to json array
j = json.dumps(data)

# or write to a file
with open('data.json', 'w') as f:
    json.dump(data, f)

Your JSON file is incorrect. Normally you must have a structure as:

{
    "key1": [
        {
            "id": "blabla",
            "name": "Toto"
        },
        {
            "id": "blibli",
            "name": "Tata"
        }
    ],
    "key2": {
        "id": "value"
    },
    "key3": "value"
}

So I think you have to change your JSON array for example as following:

{
    [
        {
            "id": 0,
            "organizer": "Some Name",
            "eventStart": "09:30 AM",
            "eventEnd": "10:00 AM",
            "subject": "rental procedure",
            "attendees": "Some Name<br />Person 2<br />Person 3"
        },
        {
            "id": 1,
            "organizer": "Some Name",
            "eventStart": "09:30 AM",
            "eventEnd": "10:00 AM",
            "subject": "rental procedure",
            "attendees": "Some Name<br />Person 2<br />Person 3"
        },
        {
            "id": 2,
            "organizer": "Some Name",
            "eventStart": "09:30 AM",
            "eventEnd": "10:00 AM",
            "subject": "rental procedure",
            "attendees": "Some Name<br />Person 2<br />Person 3"
        }
    ]
}

You can decide also to have not a list of dictionary as I proposed above but to use the ID value as key for each dictionary; in that case you have:

{
    "id0":{       
            "organizer": "Some Name",
            "eventStart": "09:30 AM",
            "eventEnd": "10:00 AM",
            "subject": "rental procedure",
            "attendees": "Some Name<br />Person 2<br />Person 3"
    },
    "id1":{       
            "organizer": "Some Name",
            "eventStart": "09:30 AM",
            "eventEnd": "10:00 AM",
            "subject": "rental procedure",
            "attendees": "Some Name<br />Person 2<br />Person 3"
    },
    "id2":{       
            "organizer": "Some Name",
            "eventStart": "09:30 AM",
            "eventEnd": "10:00 AM",
            "subject": "rental procedure",
            "attendees": "Some Name<br />Person 2<br />Person 3"
    }
}

As explained by others (in answers) you should create a new dictionary for each item on the list elsewhere you reference always the same dictionary

import json
part_nums = ['ECA-1EHG102','CL05B103KB5NNNC','CC0402KRX5R8BB104']

def json_list(list):
    lst = []
    for pn in list:
        d = {}
        d['mpn']=pn
        lst.append(d)
    return json.dumps(lst)

print json_list(part_nums)

print

[{"mpn": "ECA-1EHG102"}, {"mpn": "CL05B103KB5NNNC"}, {"mpn": "CC0402KRX5R8BB104"}]

You are mutating the same image_dict object, which in turn modifies existing references to that object (i.e. previous dictionary values).

Why do you avoid constructing a new dict? It is the only way to create separate dictionaries.

Alternatively you can move image_dict = {} into the for loop:

...
for image in images:
    image_dict = {}
    image_dict['type']= image.image_type
    ...

JSON doesn't allow extra commas at the end of an array or object. But your code adds such an extra comma. If you look at the official grammar here, you can only have a , before another value. And Python's json library conforms to that grammar, so:

>>> json.loads('[1, 2, 3, ]')
ValueError: Expecting value: line 1 column 8 (char 7)

To fix this, you could do something like this:

first = True
for task in l:
    if (task['Name'] == 'dinner'):  #criteria for desirable tasks
        if first:
            first = False
        else:
            a.write(',')
        j = json.dumps(task)
        a.write(str(j))   

On the other hand, if memory isn't an issue, it might be simpler—and certainly cleaner—to just add all of the objects to a list and then json.dumps that list:

output = []
for task in l:
    if (task['Name'] == 'dinner'):  #criteria for desirable tasks
        output.append(task)
a.write(json.dumps(output))

Or, more simply:

json.dump([task for task in l if task['Name'] == 'dinner'], a)

(In fact, even if memory is an issue, you can extend JSONEncoder, as shown in the docs, to handle iterators by converting them lazily into JSON arrays, but this is a bit tricky, so I won't show the details unless someone needs them.)

You can simply create a dictionary containing the values you are after and then convert it to json using json.dumps

import json
data = {}
data['a'] = ["12","34","23"]
data['b'] = ["13","14","45"]
json_data = json.dumps(data)
print json_data

Why not this?

// Get your values however rou want, this is just a example
var names = ["bob", "joe", "jim"];

//Initiate a empty array that holds the results
var nameObjs = [];

//Loop over input.
for (var i = 0; i < names.length; i++) {
    nameObjs.push({"name": names[i]}); //Pushes a object to the results with a key whose value is the value of the source at the current index
}