pymongo insert_many对现有文档进行突变

Question

tweets = pd.read_csv("FIFA.csv")
documents = tweets.to_dict(orient='records')
pprint(documents[0])
conn = pymongo.MongoClient("localhost")
coll = conn["test"]["tweets"]
coll.insert_many(documents, ordered=False)
pprint(documents[0])

Strangely running this code on Mongo 4.0 and pymongo 3.7.2 modifies documents .

After insert_many call there's a '_id' field which is populated in documents.

Answer 1

It's not "strangely", it's by design. http://api.mongodb.com/python/current/tutorial.html#inserting-a-document :

When a document is inserted a special key, "_id", is automatically added if the document doesn't already contain an "_id" key.