Pymongo与项目聚合

Question

我有一个非常基本的问题，

相当于Pymongo的

select name, surname, CONCAT(name, surname)
from db

Answer 1

将mongo db集合添加到db对象。它有效

concat_results = db.aggregate(
   [
      { "$project": { "NewFieldName": { "$concat": [ "$name", "$surname" ] } ,"name":True,"name":surname} }
   ]
);

for concat_result in concat_results:
    print("name":concat_result["name"],"surname":concat_result["name"],"NewFieldName":concat_result["NewFieldName"])