pymongo中使用大于、小于、大于等于、小于等于的查询方法

from bson.objectid import ObjectId
import pymongo
#查询代码
#连接本机mongodb
conn=pymongo.Connection()
#指定数据库
db = conn.books
#指定collection
collection = db.book
#大于
collection.find({'_id':{'$gt':ObjectId('51f6126139ecbb1db4a75667')}})
#大于等于
collection.find({'_id':{'$gte':ObjectId('51f6126139ecbb1db4a75667')}})
#小于
collection.find({'_id':{'$lt':ObjectId('51f6126139ecbb1db4a75667')}})
#小于等于
collection.find({'_id':{'$lte':ObjectId('51f6126139ecbb1db4a75667')}})