Delete the last four characters in the same field in all documents in mongodb with Python

I have the following document structure in mongodb in one collection:

Company = {
    name : Google
    sector : tech
    id_number: 12345XYZ5
    ...
}

I need to delete the last four characters of the field id_number (XYZ5) so that this field matches the field of another collection, that I will have to do a lookup. In the other collection, Google has the id_number 1234.

How can I do that with Python?

My guess is that it works over update_many, but I don’t know how I can delete the last four characters in the specific field in all the documents of a collection.

>Solution :

You can use the $substr operator to get the first 4 characters of the id_number field and then use the $set operator to update the id_number field with the new value.

db.collection.update_many({}, {'$set': {'id_number': {'$substr': ['$id_number', 0, 4]}}})