Convert JSON element to array

Question

I'm new to Python and haven't been coding for a while. Is there a way to convert a element in a JSON structure to an array?

Example

Given:

{
    "persons": 
        {
            "city": "Seattle", 
            "name": "Brian"
        }
}

Required:

{
    "persons": [
        {
            "city": "Seattle", 
            "name": "Brian"
        }
    ]
}

Background: I want to insert a JSON into a Big Query Table using repeating records. But the fields are not required to be repeating, it just happens in some cases. As soon I have a array everything works fine, if the array is missing, an error is returned. Now I'm looking for some python function where I just can say make my persons element an array with one element.

Best regards

Edit:

to get a bit more concrete: My structure looks like following.

{
"a" : {
    "b" : [
        {
            "c" : {
                "foo" : "bar",
                ...
            },
            "d" : {
                "foo" : "bar",
                ...
            },
            "e" : "bar"
        },
        {
            "c" : [
                {
                    "foo" : "bar",
                    ...
                },
                {
                    "foo" : "bar",
                    ...
                },
                {
                    "foo" : "bar",
                    ...
                },
                {
                    "foo" : "bar",
                    ...
                },
                {
                    "foo" : "bar",
                    ...
                }
            ],
            "d" : {
                "foo" : "bar",
                    ...
            },
            "e" : "bar"
        },
        {
            "c" : {
                "foo" : "bar",
                ...
            },
            "d" : {
                "foo" : "bar",
                ...
            },
            "e" : "bar"
        }
    ]
},
"f" : {
    "foo" : "bar",
    ....
}

}

b and c can be repeated but they don't have to. Anyway I need both of the elements as an array. Best way would be a reusable function with the JSON, b and c as input as we have different JSON files with different structures.

Currently I try to use @ajrwhite approach to achieve my requierements but I'm struggeling a bit.

Answer 1

You can change the particular element to list and re-assign:

j_data = {
    "persons":
        {
            "city": "Seattle",
            "name": "Brian"
        }
}

j_data['persons'] = [j_data['persons']]
print(j_data)

OUTPUT:

{'persons': [{'city': 'Seattle', 'name': 'Brian'}]}

Pretty printing with the indent parameter:

j_data = {
    "persons":
        {
            "city": "Seattle",
            "name": "Brian"
        }
}

j_data['persons'] = [j_data['persons']]
import json
print(json.dumps(j_data, indent=4, sort_keys=True))

OUTPUT:

{
    "persons": [
        {
            "city": "Seattle",
            "name": "Brian"
        }
    ]
}

EDIT:

Incase you want to convert all the elements to list, a simple loop would do it:

j_data = {
    "persons":
        {
            "city": "Seattle",
            "name": "Brian"
        },
    "cars":
        {
            "car1": "Tesla",
            "car2": "Toyota"
        }
}

for elem in j_data:
    j_data[elem] = [j_data[elem]]
# print(j_data)
import json
print(json.dumps(j_data, indent=4, sort_keys=True))

OUTPUT:

{      
    "persons": [
        {
            "city": "Seattle",
            "name": "Brian"
        }
    ],
     "cars": [
        {
            "car1": "Tesla",
            "car2": "Toyota"
        }
    ]
}

Answer 2

This is a common issue with working with deeply-nested JSON-style structures in Python (e.g. with MongoDB extracts).

Here is a recursive approach which wraps all dicts contained within one large dict in []:

def listify_dict(var):
    if isinstance(var, dict):
        output_dict = var.copy()
        for k, v in var.items():
            output_dict[k] = listify_dict(v)
        return [output_dict]
    elif isinstance(var, list):
        output_list = var.copy()
        for i, v in enumerate(output_list):
            output_list[i] = listify_dict(v)
        return output_list
    else:
        return var

Example:

test = {
    "persons": 
        {
            "city": "Seattle", 
            "name": "Brian"
        }
}
listify_dict(test)

Output:

[{'persons': [{'city': 'Seattle', 'name': 'Brian'}]}]