Develop Reference

Python MongoDB Find One

I am trying to find by id a document in the database, but I get None. What am I doing wrong?
python:
card = mongo.db['grl'].find_one({'id': 448510476})
or:
card = mongo.db['grl'].find_one({'id': '448510476'})
document:
{"_id":{"$oid":"5f25b1d787fc4c34a7d9aabe"},
"id":{"$numberInt":"448510476"},"first_name":"Arc","last_name":"Fl"}

I'm not sure how you are initializing your database but try this:
from pymongo import MongoClient
client = MongoClient("mongodb://127.0.0.1:27017")
db = client.database #Selecting database named "database"
#find one in collection named "collection"
card = db.collection.find_one({"id": "448510476"})
print(card)

Deleting documents from collection in Pymongo?

I have the following:
from pymongo import MongoClient
client = MongoClient()
db=client.localhost
collection=db['accounts']
db.collection.remove({})
cursor = collection.find({})
for document in cursor:
print(document)
This second part is to just print all the documents in the collection. However, the collection isn't clearing every time I rerun the program. Does anyone know why?

Just do this
db.accounts.drop()

Instead of
db.collection.remove({})
you can try this
collection.delete_many({})
Hope that solves your problem.

Instead of doing this
db.collection.remove({})
do this
db.accounts.remove({})
Also you won't need this line collection=db['accounts']
If you want dynamic collection name, you can do the following:
collection_name = 'accounts'
getattr(db, collection_name).remove({})

SQLAlchemy Postgres query is key exists in JSON

I have a model Definition:
class Definition:
meta = Column(MutableDict.as_mutable(JSON))
It stores any JSON so I want to query if a given key exists in this field.
I need something like:
defs = db.query(Definition).filter(
Definition.meta.has_key('translation')).all()
MySQL for example has a function named json_contains and I could use it:
defs = db.query(Definition).filter(
func.json_contains(
Definition.meta, 'translation') == 1).all()
How can I achieve this in PostgreSQL

Whenever I am unsure of how to use the sqlalchemy bits, I hack a version together, and go from there:
json_select = '''SELECT jdoc->'key_name1', jdoc->'translation'
FROM Definition
WHERE jdoc #> '{"translation": 1, "key_name1": "hello there"}'
;
'''
print([x for x in db.engine.execute(json_select)])
note:
psycopg2 changed in version 2.5.4: added jsonb support.
Referenced:
http://initd.org/psycopg/docs/extras.html#json-adaptation
https://www.postgresql.org/docs/9.4/static/datatype-json.html

How to do bulk insert with ordered false in mongoengine

I'm trying to insert documents in bulk, I have created a unique index in my collection and want to skip documents which are duplicate while doing bulk insertion. This can be accomplished with native mongodb function:
db.collection.insert(
<document or array of documents>,
{
ordered: <boolean>
}
)
I want to accomplish this with mongoengine, If anybody knows how to achieve this, please answer the question, thanks.

If you have a class like this:
class Foo(db.Document):
bar= db.StringField()
meta = {'indexes': [{'fields': ['bar'], 'unique': True}]}
And having a list with Foo instances foos=[Foo('a'), Foo('a'), Foo('a')]
and trying Foo.objects.insert(foos) you will get mongoengine.errors.NotUniqueError
1st woraround would be delete index from mongodb, insert duplicates, and than ensure index with {unique : true, dropDups : true}
2nd workaround would be using underlying pymongo API for bulk ops: https://docs.mongodb.com/manual/reference/method/db.collection.initializeOrderedBulkOp/#db.collection.initializeOrderedBulkOp

For now I am using raw pymongo from mongoengine as a workaround for this. This is the 2nd workaround that #Alexey Smirnov mentioned. So for a mongoengine Document class DocClass you will access the underlying pymongo collection and execute query like below:
from pymongo.errors import BulkWriteError
try:
doc_list = [doc.to_mongo() for doc in me_doc_list] # Convert ME objects to what pymongo can understand
DocClass._get_collection().insert_many(doc_list, ordered=False)
except BulkWriteError as bwe:
print("Batch Inserted with some errors. May be some duplicates were found and are skipped.")
print(f"Count is {DocClass.objects.count()}.")
except Exception as e:
print( { 'error': str(e) })

Get all documents of a collection using Pymongo

I want to write a function to return all the documents contained in mycollection in mongodb
from pymongo import MongoClient
if __name__ == '__main__':
client = MongoClient("localhost", 27017, maxPoolSize=50)
db=client.mydatabase
collection=db['mycollection']
cursor = collection.find({})
for document in cursor:
print(document)
However, the function returns: Process finished with exit code 0

Here is the sample code which works fine when you run from command prompt.
from pymongo import MongoClient
if __name__ == '__main__':
client = MongoClient("localhost", 27017, maxPoolSize=50)
db = client.localhost
collection = db['chain']
cursor = collection.find({})
for document in cursor:
print(document)
Please check the collection name.

pymongo creates a cursor. Hence you'll get the object 'under' the cursor. To get all objects in general try:
list(db.collection.find({}))
This will force the cursor to iterate over each object and put it in a list()
Have fun...

I think this will work fine in your program.
cursor = db.mycollection # choosing the collection you need
for document in cursor.find():
print (document)

it works fine for me,try checking the exact database name and collection name.
and try changing from db=client.mydatabase to db=client['mydatabase'] .
If your database name is such that using attribute style access won’t work (like test-database), you can use dictionary style access instead.
source !