MongoDB/PyMongo:如何在Map函数中使用点表示法？

pip install pymongo

from pymongo import MongoClient

# 连接到MongoDB数据库
client = MongoClient("mongodb://localhost:27017/")
db = client["my_database"]
collection = db["my_collection"]

# 假设我们的文档结构如下
document = {
    "name": "John",
    "age": 30,
    "address": {
        "city": "New York",
        "state": "NY"
    }
}

# 插入一个文档
collection.insert_one(document)

# 使用点表示法在Map函数中访问嵌套属性
result = collection.aggregate([
    {
        "$project": {
            "name": 1,
            "age": 1,
            "city": "$address.city"
        }
    }
])

# 输出结果
for item in result:
    print(item)