如何用python pymongo在mongodb查询中查找$avg

from pymongo import MongoClient

# 连接MongoDB数据库
client = MongoClient('mongodb://localhost:27017/')
db = client['your_database']  # 替换为实际的数据库名称
collection = db['your_collection']  # 替换为实际的集合名称

# 构建查询条件
query = [
    {
        '$group': {
            '_id': None,
            'average_field': {'$avg': '$field_name'}  # 替换为实际的字段名称
        }
    }
]

# 执行查询
result = list(collection.aggregate(query))

# 输出结果
if result:
    average_value = result[0]['average_field']
    print(f"The average value of 'field_name' is: {average_value}")
else:
    print("No documents found")

# 关闭数据库连接
client.close()