I execute some_python_function on all elements of collection.
This function returns different values for each document.

I developed the following function, but it’s very slow.

for doc in db.collection.find(query, projection):
    result = db.collection.update_one(
        {"_id": doc["_id"]}, 
        {"$set": {"field": some_python_function(doc["field"])}}
    )

I am looking any smarter way to do it, rather than updating documents one-by-one.

What would you recommend?

EDIT:
I have just found bulk operations in the API:
https://pymongo.readthedocs.io/en/stable/examples/bulk.html

updates = []
for doc in db.collection.find(filter, projection):
    if doc.get("titles"):
        updates.append(
            UpdateOne(
                {"_id": doc["_id"]}, {"$set": {"field": some_python_function(doc["field"]}}
            )
        )
result = collection.bulk_write(updates)

>Solution :

Use bulkWrite to write multiples document at once.

Here is an answer for a similar question.