Note that the methods in this answer have been deprecated. See Sid Holland's answer for more details.
refer the documentation,
for example
db.update({"_id": acs_num}, {"$set": mydata}, upsert = True)
or find_and_modify
according to docs says Returns either the object before or after modification based on new parameter. If no objects match the query and upsert is false, returns None. If upserting and new is false, returns {}
for example:
In [1]: from pymongo import MongoClient
In [2]: client = MongoClient("mongodb://localhost:27017")
...: db = client["testdb"]
...: mycollection = db["mydb"]
...:
In [3]: import datetime
...: post1 = {"author": "Mike", "text": "My first blog post!", "tags": ["mongodb", "python", "pymongo"], "date": datetime.datetime.utcnow()}
...:
In [4]: mycollection.insert(post1)
Out[4]: ObjectId('535fd580c314f91d28c35ee1')
In [5]: [x for x in mycollection.find()]
Out[5]:
[{u'_id': ObjectId('535fd580c314f91d28c35ee1'),
u'author': u'Mike',
u'date': datetime.datetime(2014, 4, 29, 16, 38, 15, 457000),
u'tags': [u'mongodb', u'python', u'pymongo'],
u'text': u'My first blog post!'}]
In [6]: mycollection.find_and_modify(query={'author':'Mike'}, update={"$set": {'author': "Mike2"}}, upsert=False, full_response= True)
Out[6]:
{u'lastErrorObject': {u'n': 1, u'updatedExisting': True},
u'ok': 1.0,
u'value': {u'_id': ObjectId('535fd580c314f91d28c35ee1'),
u'author': u'Mike',
u'date': datetime.datetime(2014, 4, 29, 16, 38, 15, 457000),
u'tags': [u'mongodb', u'python', u'pymongo'],
u'text': u'My first blog post!'}}
In [7]: [ x for x in mycollection.find()]
Out[7]:
[{u'_id': ObjectId('535fd580c314f91d28c35ee1'),
u'author': u'Mike2',
u'date': datetime.datetime(2014, 4, 29, 16, 38, 15, 457000),
u'tags': [u'mongodb', u'python', u'pymongo'],
u'text': u'My first blog post!'}]