How do I do a get_or_create in pymongo (python mongodb)?

First, find if 开发者_如何学Pythona document matching query exists.

If so, update that document with the new data.

Otherwise, insert a new document into the database.

You can use "upsert" equal to true. Then the update query you run with "upsert" as true will do exactly what you want.

• update if exists.
• insert new if it does not exist.

From MongoDb documentation:

db.collection.update( criteria, objNew, upsert, multi )

Arguments:

    criteria - query which selects the record to update;
    objNew - updated object or $ operators (e.g., $inc) which manipulate the object
    upsert - if this should be an "upsert"; that is, if the record does not exist, insert it
    multi - if all documents matching criteria should be updated

http://www.mongodb.org/display/DOCS/Updating

Example:

db.test.update({"x": "42"}, {"$set": {"a": "21"}},True)    
#True => Upsert is True

See "update" documentation here :

http://api.mongodb.org/python/current/api/pymongo/collection.html

http://api.mongodb.org/python/current/api/pymongo/collection.html#pymongo.collection.Collection.update

Set upsert=True

Full test example. Also see $setOnInsert which unlike $set will not alter the record if the key exists.

payload= {'id':'key123','other':'stuff'}
collection.update({'eventid':payload['id']}, {"$set": payload}, upsert=True)
collection.count_documents({}) # 1

payload= {'id':'key123','other':'stuff2'}
collection.update({'eventid':payload['id']}, {"$set": payload}, upsert=True)
collection.count_documents({}) # 1

payload= {'id':'key456','other':'more stuff'}
collection.update({'eventid':payload['id']}, {"$setOnInsert": payload}, upsert=True)
collection.count_documents({}) # 2

payload= {'id':'key456','other':'more stuff2'}
collection.update({'eventid':payload['id']}, {"$setOnInsert": payload}, upsert=True)
collection.count_documents({})