Why does it return immutable records?

Question

Python

import pymongo

conn = pymongo.MongoClient("localhost", 27017)
db = conn["crypto_signals"]
signals_db = db["signals"]
signals_db.update({}, {"$set": {"priority": 0}}, )
signals = signals_db.find({"priority":{"$exists":False}})

for signal in signals:
    print(signal)

The print command returns the part of the records that has not been changed, the priority field is missing.

Answer 1

update should be replaced with update_many
And everything will work