helpers.py

def qs_to_dict(qs, exclude=(), func=None):
    return [model_to_dict(model, exclude, func) for model in qs]

def model_to_dict(model, exclude=(), func=None):
    result = {}
    fields = [field.name for field in model._meta.fields if field.name not in exclude]
    if callable(func):
        for field in fields:
            key = func(field)
            if key:
                result[key] = getattr(model, field)
    else:
        for field in fields:
            result[field] = getattr(model, field)
    return result

test.py

def my_filter(key):
    if key in ('id', 'email'):
        return key.upper()
    else:
        # return None to not be included
        return None

qs_to_dict(User.objects.all(), exclude=('avatar',), func=my_filter)
qs_to_dict(User.objects.all(), func=lambda field: field.upper())