python 2.7 - Update with pull in MongoDB 3.2.5 matching but not modifying document -

i getting 500 error on getjson request maps python 2.7 function containing mongodb update $pull.

last error seen sudo tail -f /var/log/apache2/error.log is:

[wsgi:error] [pid 1721:tid 140612911712000]  [client 127.0.0.1:59078]  keyerror: 'nmodified', referer: http://localhost/control_room 

the python logic deals particular key update $pull:

update_with_pull = collection.update({"user_email":user_email,"top_level.year":entry_year,"top_level.month":entry_month}, { "$pull": {dynamic_nested_key: {"timestamp":entry_timestamp}}}) 

the conditional after trying catch if document has been modified or not with:

if update_with_pull['nmodified'] == 1:   #do stuff 

i tested same operation in mongo shell , returned:

writeresult({ "nmatched" : 1, "nupserted" : 0, "nmodified" : 0 }) 

so seems matching query not doing modifications.

to further troubleshoot, entry_timestamp value used in $pull section above consistent in database , function (ie both strings same characters).

some ideas:

• i've moved application 2.6.11 3.2.5 mongodb environment, may causing problem, but, if so, haven't been able ascertain how yet.
• the syntax $pull has changed in 3.2.5?
• there permission issues on collection preventing modification?
• i'm running pymongo 2.6.2 in virtualenv - perhaps has incompatibilities mongodb 3.2.5?

solution

upgrading pymongo 3.2.2 causes error:

serverselectiontimeouterror: no servers found yet 

https://stackoverflow.com/a/31194981/1063287

however, upgraded pymongo 2.8, restarted apache , problem seems resolved.