Question

I am serializing multiple nested dictionaries to JSON using Python with simplejson.

Is there any way to automatically exclude empty/null values?

For example, serialize this:

 {
     "dict1" : {
     "key1" : "value1",
     "key2" : None
     }
 }

to

 {
     "dict1" : {
     "key1" : "value1"
     }
 }

When using Jackson with Java you can use Inclusion.NON_NULL to do this. Is there a simplejson equivalent?

Answer 1

def del_none(d):
    """
    Delete keys with the value ``None`` in a dictionary, recursively.

    This alters the input so you may wish to ``copy`` the dict first.
    """
    # For Python 3, write `list(d.items())`; `d.items()` won’t work
    # For Python 2, write `d.items()`; `d.iteritems()` won’t work
    for key, value in list(d.items()):
        if value is None:
            del d[key]
        elif isinstance(value, dict):
            del_none(value)
    return d  # For convenience

Sample usage:

>>> mydict = {'dict1': {'key1': 'value1', 'key2': None}}
>>> print(del_none(mydict.copy()))
{'dict1': {'key1': 'value1'}}

Then you can feed that to json.