MongoDB InvalidDocument: Cannot encode object

Question

I am using scrapy to scrap blogs and then store the data in mongodb. At first i got the InvalidDocument Exception. So obvious to me is that the data is not in the right encoding

Answer 1

Finally I figured it out. The problem was not with encoding. It was with the structure of the documents.

Because i went off on the standard MongoPipeline example which does not deal with nested scrapy items.

What i am doing is: BlogItem: "url" ... comments = [CommentItem]

So my BlogItem has a list of CommentItems. Now the problem came here, for persisting the object in the database i do:

self.db[self.collection_name].insert(dict(item))

So here i am parsing the BlogItem to a dict. But i am not parsing the list of CommentItems. And because the traceback displays the CommentItem kind of like a dict, It did not occur to me that the problematic object is not a dict!

So finally the the way to fix this problem is to change the line when appending the comment to the comment list as such:

item['comments'].append(dict(comment))

Now MongoDB considers it as a valid document.

Lastly, for the last part where i ask why i am getting a exception on the python console and not in the script.

The reason is because i was working on the python console, which only supports ascii. And thus the error.

Answer 2

I ran into the same error using a numpy array in a Mongo query :

'myField' : { '$in': myList },

The fix was simply to convert the nd.array() into a list :

'myField' : { '$in': list(myList) },

Answer 3

I got this error when running a query

db.collection.find({'attr': {'$gte': 20}})

and some records in collection had a non-numeric value for attr.

Answer 4

First, when you do "somestring".encode(...), isn't changing "somestring", but it returns a new encoded string, so you should use something like:

 item['author'] = item['author'].encode('utf-8', 'strict')

and the same for the other fields.