Flattens a nested dictionary so that it can be more easily posted as multipart/form-data. Helpful especially with unit tests, requests.post, etc

form_data_flattener.py

def flatten_dict_for_formdata(input_dict, array_separator="[{i}]"):
    """
    Recursively flattens nested dict()s into a single level suitable for passing to a library
    that makes multipart/form-data posts.
    - nested dicts, tuples (treated like arrays), lists, list of objects, etc
        {
            "owner": {
                "name": {"first": "andy"},
                "favorite_color": ("blue", "green")
            },
            "superpower": "talks to snails",
            "funiture": [
                {
                    "id": "table",
                    "subparts": [
                        {
                            "type": "leg",
                            "qty": 7,
                            "parts": ["wood", "metal", "screws"]
                        }
                    ]
                }
            ]
        }
        ---------------------------------------------------------
        "owner.favorite_color[0]": "blue", 
        "owner.favorite_color[1]": "green", 
        "owner.name.first": "andy", 
        "funiture[0]subparts[0]parts[0]": "wood", 
        "funiture[0]subparts[0]parts[1]": "metal", 
        "funiture[0]subparts[0]parts[2]": "screws", 
        "funiture[0]subparts[0]type": "leg", 
        "funiture[0]subparts[0]qty": 7, 
        "funiture[0]id": "table", 
        "superpower": "talks to snails"
    """

    def __flatten(value, prefix, result_dict, previous=None):
        """
        Nested function to prevent the main interface from having to have "optional" paramters
        that must always be null on first call (e.g. prefix & result_dict).
        """
        if isinstance(value, dict):
            # If we just processed a dict, then separate the the new members with a dot.
            # We don't want to do this if it is an object inside an array.  in that case there
            # is no separator, the [x] _is_ the separator, adding a "." like list[1].name will break
            # but list[x]name is correct (at least for DRF/django decoding)
            if previous == "dict":
                prefix += "."

            for key, v in value.iteritems():
                __flatten(
                    value=v,
                    prefix=prefix + key,
                    result_dict=result_dict,
                    previous="dict"
                )
        elif isinstance(value, (list, tuple)):
            for i, v in enumerate(value):
                __flatten(
                    value=v,
                    prefix=prefix + array_separator.format(i=i),  # e.g. name[1]
                    result_dict=result_dict,
                    previous="array"
                )
        else:
            result_dict[prefix] = value
            
        return result_dict

    # invoke the inner recursive function
    return __flatten(input_dict, '', {})