Pymongo:iterating dictionary of a list of dictionary

Question

Let us say I have a big collection including documents such as these:

{"_id": 0, 
"name":"John Doe",
"items": [
     {"x":5,
      "y":8,
      "z":9},
     {"x":4,
      "y":2,
      "z":1},
     {"x":3,
      "y":5,
      "z":8}
]
}

I am fetching the collection into a variable called 'data' with pymongo and trying to iterate over the items in order to update some. I have tried to print those values with the following code:

for i in data:
    for j in data[i].get("items"):
        pprint(j.get("x"))

and it gave an error:

pymongo.errors.InvalidOperation: cannot set options after executing query

Even if I get the items, I do not see a way to change data. Why is this happening and how can I iterate through items and change their values?

Answer 1

How looks db query?

Try something like this for iteration:

cursor = db.get_collection('some_collection').find()

for doc in cursor:
    for item in doc['items']:
        pprint(item.get('x'))

Answer 2

Let's say if you want to change the values of all x .

for i in data.get('items'):
    # to change the values in items
    # this will replace all values of key x
    i['x'] = new_value

simply assign a new value to items key.