How can I overcome "datetime.datetime not JSON serializable"?

json, python

Solution

Updated for 2018

The original answer accommodated the way MongoDB "date" fields were represented as:

`{"$date": 1506816000000}`

If you want a generic Python solution for serializing `datetime` to json, check out @jjmontes' answer for a quick solution which requires no dependencies.

As you are using mongoengine (per comments) and pymongo is a dependency, pymongo has built-in utilities to help with json serialization: http://api.mongodb.org/python/1.10.1/api/bson/json_util.html

Example usage (serialization):

from bson import json_util
import json

json.dumps(anObject, default=json_util.default)

Example usage (deserialization):

json.loads(aJsonString, object_hook=json_util.object_hook)

Django

Django provides a native `DjangoJSONEncoder` serializer that deals with this kind of properly.

See https://docs.djangoproject.com/en/dev/topics/serialization/#djangojsonencoder

from django.core.serializers.json import DjangoJSONEncoder

return json.dumps(
  item,
  sort_keys=True,
  indent=1,
  cls=DjangoJSONEncoder
)

One difference I've noticed between `DjangoJSONEncoder` and using a custom `default` like this:

import datetime
import json

def default(o):
    if isinstance(o, (datetime.date, datetime.datetime)):
        return o.isoformat()

return json.dumps(
  item,
  sort_keys=True,
  indent=1,
  default=default
)

Is that Django strips a bit of the data:

 "last_login": "2018-08-03T10:51:42.990", # DjangoJSONEncoder 
 "last_login": "2018-08-03T10:51:42.990239", # default

So, you may need to be careful about that in some cases.

Problem

I have a basic dict as follows: ``` sample = {} sample['title'] = "String" sample['somedate'] = somedatetimehere ``` When I try to do `jsonify(sample)` I get: TypeError: datetime.datetime(2012, 8, 8, 21, 46, 24, 862000) is not JSON serializable What can I do such that my dictionary sample can overcome the error above? Note: Though it may not be relevant, the dictionaries are generated from the retrieval of records out of `mongodb` where when I print out `str(sample['somedate'])`, the output is `2012-08-08 21:46:24.862000`.

Original source

Related problems