pymongo syntax to update a subdocument

Question

My documents look like this:

{
  a: "..."
  subdocs [
    {
      l: "..."
      m: "..."
      n: 0
    },
    {
      l: "..."
      m: "..."
      n: 0
    }

  }
}

I have to update the 'n' field in a particular subdoc using pymongo. I have the document and the index of the subdocument so I can get the subdoc like this

subdoc = mydoc['subdocs'][index]

I try to do an update through pymongo

coll.update( { mydoc['subdocs'][index] : subdoc }, { "$inc": { n: 1 }} )

I get this exception

<type 'exceptions.TypeError'>

I've tried several variations on this and can't get the pymongo syntax right. I think my query document is incorrect. What does pymongo expect for this syntax?

JohnnyHK JohnnyHK · Accepted Answer · 2012-12-15T19:17:08

You need to identify the array element to update in the second parameter to update using dot notation like this:

coll.update({'_id': mydoc['_id']}, {'$inc': {'subdocs.' + str(index) + '.n': 1}})

pymongo syntax to update a subdocument

1 Answers