插入 Mongo 文档后如何更新它？

假设我插入文档。

post = { some dictionary }
mongo_id = mycollection.insert(post)

现在，假设我想添加一个字段并对其进行更新。我该怎么做？这好像不管用... ..。

post = mycollection.find_one({"_id":mongo_id})
post['newfield'] = "abc"
mycollection.save(post)
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最佳答案

In pymongo you can update with:

mycollection.update({'_id':mongo_id}, {"$set": post}, upsert=False)

Upsert parameter will insert instead of updating if the post is not found in the database.
Documentation is available at mongodb site.

UPDATE For version > 3 use update_one instead of update:

mycollection.update_one({'_id':mongo_id}, {"$set": post}, upsert=False)
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I will use collection.save(the_changed_dict) this way. I've just tested this, and it still works for me. The following is quoted directly from pymongo doc.:

save(to_save[, manipulate=True[, safe=False[, **kwargs]]])

Save a document in this collection.

If to_save already has an "_id" then an update() (upsert) operation is performed and any existing document with that "_id" is overwritten. Otherwise an insert() operation is performed. In this case if manipulate is True an "_id" will be added to to_save and this method returns the "_id" of the saved document. If manipulate is False the "_id" will be added by the server but this method will return None.

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This is an old question, but I stumbled onto this when looking for the answer so I wanted to give the update to the answer for reference.

The methods save and update are deprecated.

save(to_save, manipulate=True, check_keys=True, **kwargs)¶ Save a document in this collection.

DEPRECATED - Use insert_one() or replace_one() instead.

Changed in version 3.0: Removed the safe parameter. Pass w=0 for unacknowledged write operations.

update(spec, document, upsert=False, manipulate=False, multi=False, check_keys=True, **kwargs) Update a document(s) in this collection.

DEPRECATED - Use replace_one(), update_one(), or update_many() instead.

Changed in version 3.0: Removed the safe parameter. Pass w=0 for unacknowledged write operations.

in the OPs particular case, it's better to use replace_one.

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According to the latest documentation about PyMongo titled Insert a Document (insert is deprecated) and following defensive approach, you should insert and update as follows:

result = mycollection.insert_one(post)
post = mycollection.find_one({'_id': result.inserted_id})


if post is not None:
post['newfield'] = "abc"
mycollection.save(post)
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mycollection.find_one_and_update({"_id": mongo_id},
{"$set": {"newfield": "abc"}})

should work splendidly for you. If there is no document of id mongo_id, it will fail, unless you also use upsert=True. This returns the old document by default. To get the new one, pass return_document=ReturnDocument.AFTER. All parameters are described in the API.

The method was introduced for MongoDB 3.0. It was extended for 3.2, 3.4, and 3.6.


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