mapper.py

import json


def mapper(source, template):

    def _get(d, keys, splitter="."):
        if isinstance(keys, str):
            keys = keys.split(splitter)[1:]
        if not keys or d is None:
            return d
        return _get(d.get(keys[0]), keys[1:])

    def _map(d=template):
        o = {}
        for k, v in d.items():
            if isinstance(v, dict):
                o[k] = _map(v)
            else:
                o[k] = _get(source, v)
        return o

    return _map(d=template)


source = {
    "name": "ghelo",
    "age": 18,
    "address": {
        "house_no": "1234",
        "street": "Hollywood Blvd",
        "city": "Los Angeles",
        "area_code": "54321"
    },
    "socmed": {
        "fb": {
            "username": "ghelobytes"
        },
        "twitter": {
            "handle": "@ghelobytes"
        },
        "gamestop": {
            "sources":  ["coins", "elixir"]
        }
    },
    "pets": ["dog", "cat"]
}

mapping_template = {
    "name": "@src.name",
    "fb_account": "@src.socmed.fb.username",
    "twitter_account": "@src.socmed.twitter.handle",
    "user": {
        "age": "@src.age",
        "health": {
            "sources": "@src.socmed.gamestop.sources"
        }
    },
    "pet": {
        "domestic": {
            "alive": "@src.pets"
        }
    },
    "city": "@src.address.city"
}


r = mapper(source, mapping_template)
r = json.dumps(r, indent=4)
print(r)

result.json

{
    "name": "ghelo",
    "fb_account": "ghelobytes",
    "twitter_account": "@ghelobytes",
    "user": {
        "age": 18,
        "health": {
            "sources": [
                "coins",
                "elixir"
            ]
        }
    },
    "pet": {
        "domestic": {
            "alive": [
                "dog",
                "cat"
            ]
        }
    },
    "city": "Los Angeles"
}