Removing _id element from Pymongo results

Question

I'm attempting to create a web service using MongoDB and Flask (using the pymongo driver). A query to the database returns documents with the "_id" field included, of course. I don't want to send this to the client, so how do I remove it?

Here's a Flask route:

@app.route('/theobjects') def index():     objects = db.collection.find()     return str(json.dumps({'results': list(objects)},          default = json_util.default,         indent = 4)) 

This returns:

{ "results": [     {         "whatever": {             "field1": "value",              "field2": "value",          },          "whatever2": {             "field3": "value"         },         ...         "_id": {             "$oid": "..."         },       ...     } ]} 

I thought it was a dictionary and I could just delete the element before returning it:

del objects['_id'] 

But that returns a TypeError:

TypeError: 'Cursor' object does not support item deletion 

So it isn't a dictionary, but something I have to iterate over with each result as a dictionary. So I try to do that with this code:

for object in objects:     del object['_id'] 

Each object dictionary looks the way I'd like it to now, but the objects cursor is empty. So I try to create a new dictionary and after deleting _id from each, add to a new dictionary that Flask will return:

new_object = {} for object in objects:     for key, item in objects.items():         if key == '_id':             del object['_id']             new_object.update(object) 

This just returns a dictionary with the first-level keys and nothing else.

So this is sort of a standard nested dictionaries problem, but I'm also shocked that MongoDB doesn't have a way to easily deal with this.

The MongoDB documentation explains that you can exclude _id with

{ _id : 0 } 

But that does nothing with pymongo. The Pymongo documentation explains that you can list the fields you want returned, but "(“_id” will always be included)". Seriously? Is there no way around this? Is there something simple and stupid that I'm overlooking here?

Answer 1

To exclude the _id field in a find query in pymongo, you can use:

db.collection.find({}, {'_id': False}) 

The documentation is somewhat missleading on this as it says the _id field is always included. But you can exclude it like shown above.

Answer 2

Above answer fails if we want specific fields and still ignore _id. Use the following in such cases:

db.collection.find({'required_column_A':1,'required_col_B':1, '_id': False})