MongoEngine delete document

Question

I have the following MongoEngine document

{
    '_id': 'some_id',
    'data': 'some_data'
}

How can I delete this document using MongoEngine?

What I've tried:

import my_collection

obj = my_collection.MyCol.objects.get(_id='some_id')
# obj is correctly found - let's continue

obj.delete()
# mongoengine.errors.ValidationError: 'None' is not a valid ObjectId

obj.delete('some_id')
# TypeError: delete() takes 1 positional argument but 2 were given

obj.delete(_id='some_id')
# mongoengine.errors.ValidationError: 'None' is not a valid ObjectId

-- note

Oddly enough, the following works perfectly:

my_collection.MyCol.objects.delete()
# delete all documents in the collection

But I've followed MongoEngine docs, and still can't manage to delete just one specific document.

Answer 1

When referencing mongoengine ObjecIds you don't use the underscore.

obj = my_collection.MyCol.objects.get(id='some_id')

or

obj = my_collection.MyCol.objects(id='some_id')
obj.delete()

Answer 2

If your document overrides _id, you must indicate that it's still the primary key. Change your document class definition from:

class MyCol(Document):
    _id = db.StringField()
    ...

To specify the primary key:

class MyCol(Document):
    _id = db.StringField(primary_key=True)
    ...