I have a list of users users["pirates"] and they're stored in the format ['pirate1','pirate2']. If I hand the list over to a def and query for it in MongoDB, it returns data based on the first index (e.g. pirate1) only. If I hand over a list in the format ["pirate1","pirate"], it returns data based on all the elements in the list. So I think there's something wrong with the encapsulation of the elements in the list. My question: can I change the encapsulation from ' to " without replacing every ' on every element with a loop manually? Short Example: aList = list() # get pirate Stuff # users["pirates"] is a list returned by a former query # so e.g. users["pirates"][0] may be peter without any quotes for pirate in users["pirates"]: aList.append(pirate) aVar = pirateDef(aList) print(aVar) the definition: def pirateDef(inputList = list()): # prepare query col = mongoConnect().MYCOL # query for pirates Arrrr pirates = col.find({ "_id" : {"$in" : inputList}} ).sort("_id",1).limit(50) # loop over users userList = list() for person in pirates: # do stuff that has nothing to do with the problem # append user to userlist userList.append(person) return userList If the given list has ' encapsulation it returns: 'pirates': [{'pirate': 'Arrr', '_id': 'blabla'}] If capsulated with " it returns: 'pirates' : [{'_id': 'blabla', 'pirate' : 'Arrr'}, {'_id': 'blabla2', 'pirate' : 'cheers'}] EDIT: I tried figuring out, that the problem has to be in the MongoDB query. The list is handed over to the Def correctly, but after querying pirates only consists of 1 element... Thanks for helping me Codehai