Typeerror: Objectid('') Is Not JSON Serializable

TypeError: ObjectId('') is not JSON serializable

You should define you own JSONEncoder and using it:

import json
from bson import ObjectId

class JSONEncoder(json.JSONEncoder):
    def default(self, o):
        if isinstance(o, ObjectId):
            return str(o)
        return json.JSONEncoder.default(self, o)

JSONEncoder().encode(analytics)

It's also possible to use it in the following way.

json.encode(analytics, cls=JSONEncoder)

Getting 'TypeError: ObjectId('') is not JSON serializable' when using Flask 0.10.1

EDIT: Even easier fix. You don't even need to do any JSON encoding/decoding.

Just save the session['_id'] as a string:

user = db.minitwit.user.find_one({'username': request.form['username']})
session['_id'] = str(user['_id'])

And then everywhere you want to do something with the session['_id'] you have to wrap it with ObjectId() so it's passed as a ObjectId object to MongoDB.

if '_id' in session:
    g.user = db.minitwit.user.find_one({'_id': session['_id']})

to:

if '_id' in session:
    g.user = db.minitwit.user.find_one({'_id': ObjectId(session['_id'])})

You can see the full diff for the fix on my github repo.

If anyone cares to know why the 'TypeError: ObjectId('') is not JSON serializable' "issue" appeared in Flask 0.10.1, it's because they changed the way sessions are stored. They are now stored as JSON so since the '_id' object in MongoDB isn't standard JSON, it failed to serialize the session token, thus giving the TypeError. Read about the change here: http://flask.pocoo.org/docs/upgrading/#upgrading-to-010

TypeError: Object of type 'ObjectId' is not JSON serializable using Flask and MongoDB

When inserting a document into MongoDB, if you don't specify an _id field, the pymongo drivers will add an _id field of type ObjectId to the document, before inserting into the database.

See https://pymongo.readthedocs.io/en/stable/faq.html#writes-and-ids

Flask is then trying to JSON serialise the field which it doesn't know how to do; hence the error.

A simple fix could be to just pop the _id before returning it; e.g.

# insert into database 's41', collection 'links'
db_s41.links.insert_one(new_link_doc)
new_link_doc.pop('_id')

return new_link_doc

TypeError Object id is not JSON serializable

The error is because you are trying to save a model instance in the session, and the session middleware cannot serialize it to JSON.

request.session['content'] = model1object

It may be enough to store the id of the object instead of the object itself.

request.session['content_id'] = model1object.id 
...
# retrieve from db later
model1object = Model1.objects.get(id=request.session['content_id'])

If you need to store more information in the session than the id, then you'll have to convert it to a format that is JSON serializable. For a simple model, it might be easiest to create a Python dict.

request.session['content'] = {
    'id': model1object.id,
    'name': model1object.name,
    ...
}

For more complicated models, you could look at the docs on serializing Django objects.

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