Pymongo/bson: Convert python.cursor.Cursor object to serializable/JSON object

Question

New to MongoDb and Python (webapp2). So, I was fetching some data from a mongodb database. But I was unable to use json.dumps on the returned data. Here's my code:

exchangedata = db.Stock_Master.find({"Country": "PHILIPPINES"}, {"_id" : 0})        
self.response.write(json.dumps(exchangedata)) 

This throws an error:

TypeError: pymongo.cursor.Cursor object at 0x7fcd51230290 is not JSON serializable

The type of exchangedata is pymongo.cursor.Cursor. How can I convert it into a json object?

Solution 1

Use dumps from bson.json_util:

>>> c = pymongo.MongoClient()
>>> c.test.test.count()
5
>>> from bson.json_util import dumps
>>> dumps(c.test.test.find())
'[{"_id": {"$oid": "555cb3a7fa5bd85b81d5a624"}}, {"_id": {"$oid": "555cb3a7fa5bd85b81d5a625"}}, {"_id": {"$oid": "555cb3a7fa5bd85b81d5a626"}}, {"_id": {"$oid": "555cb3a7fa5bd85b81d5a627"}}, {"_id": {"$oid": "555cb3a7fa5bd85b81d5a628"}}]'

Solution 2

Simple Solution

 // Use dumps from bson.json_util:
from bson.json_util import dumps

@app.route("/")
def home_page():

    booking = dumps(mongo.db.bookings.find())
    print booking
    return  booking

Comments

[alecxe]

Related: stackoverflow.com/questions/13241878/….

[Kyle Pittman]

Convert the cursor to a list of objects: self.response.write(json.dumps(list(exchangedata)))

[Martin Konecny]

Mongo returns a cursor object instead of an actual list of data. You will need to convert that to a list first as Kyle mentioned.

[Tarun Dugar]

Not working with the list wrapper. It sends across an empty data object.

[hashark]

this solution is good only for very small dataset as it dumps all of the objects fetched by the cursor to a single string. With bigger data it doesn't help and you can as well iterate over all of the results and just save them.

[XChikuX]

bson package is really bad for large data. Use the bsonjs package instead. In most cases it should suffice for you to convert the ObjectId() alone.

[Evan Thomas]

dumps(c.test.test.find(), indent=4) is better.