MongoDB学习笔记5——Python和MongoDB

1. MongoDB使用BSON样式的文档，在Python中使用的是字典。

2.使用PyMongo模块

1）连接和断开

from pymongo import MongoClient

c = MongoClient()

db = c.library (其中library是数据库)

collection = db.items (items是集合）

2）插入数据

item = {
"Type" : "Laptop",
"ItemNumber" : "1234EXD",
"Status" : "In use",
"Location" : {
"Department" : "Development",
"Building" : "2B",
"Floor" : 12,
"Desk" : 120101,
"Owner" : "Andreson, Thomas"
},
"Tags" : ["Laptop","Development","In Use"]
}

将数据插入到集合中：

collection.insert_one(item)

如果遇到多组数据的情况：

two = [{
"Type" : "Laptop",
"ItemNumber" : "2345EXD",
"Status" : "In use",
"Location" : {
"Department" : "Development",
"Building" : "2B",
"Floor" : 12,
"Desk" : 120102,
"Owner" : "Smith, Simon"
},
"Tags" : ["Laptop", "Development", "In Use"]
},
{
"Type" : "Laptop",
"ItemNumber" : "3456TFS",
"Status" : "In use",
"Location" : {
"Department" : "Development",
"Building" : "2B",
"Floor" : 12,
"Desk" : 120103,
"Owner" : "Smith, Simon"
},
"Tags" : ["Laptop", "Development", "In Use"]
}]

使用

collection.insert_many(two)

3）搜索数据

3-1）搜索单个文档

collection.find_one() （没有其他限制条件默认返回第一个文档）

collection.find_one({"ItemNumber":"3456TFS"}, {'_id':False})（有限制条件，不显示'_id'）

3-2）搜索多个文档

for doc in collection.find():

doc

for doc in collection.find({"Location.Owner":"Andreson, Thomas"}):

doc

3-3）使用点操作符

for doc in collection.find({"Location.Department":"Development"}):

doc

3-4）返回字段

for doc in collection.find({'Status':'In use'},{'ItemNumber':True,'Location.Owner':True}):

doc

3-5）使用sort()、limit()和skip()简化查询

for doc in collection.find({'Status':'In use'},{'ItemNumber':True,'Location.Owner':True}).sort('ItemNumber'):

doc

for doc in collection.find({},{'ItemNumber':True}).limit(2):
doc

for doc in collection.find({'Status':'In use'},{'ItemNumber':True,'Location.Owner':True}).limit(2).skip(1).sort('ItemNumber'): （跳过一个，输出两个，按照要求排序）
doc

3-6）聚集查询

3-6-1）使用count()统计数目

collection.count()

3-6-2）使用distinct()统计唯一数据的数目

collection.distinct('ItemNumber') （无重复）

3-6-3）使用聚集框架对数据分组

collection.aggregate([
{'$unwind':'$Tags'},
{'$group':{'_id':'$Tags','Totals':{'$sum':1}}}
])

按照特定指示输出数据

from bson.son import SON
collection.aggregate([
{'$unwind':'$Tags'},
{'$group':{'_id':'$Tags','Totals':{'$sum':1}}},
{'$sort':SON([('Totals',-1)])}
])

3-7）使用hint()指定索引

from pymongo import ASCENDING

collection.create_index([("ItemNumber",ASCENDING)])

for doc in collection.find({"Location.Owner":"Smith, Simon"}).hint([("ItemNumber",ASCENDING)]):
doc

3-8）使用条件操作符定义查询

3-8-1）使用$lt、$gt、$lte和$gte操作符

for doc in collection.find({"Location.Desk":{"$lt":120102}}):
doc

for doc in collection.find({"Location.Desk":{"$gt":120102}}):
doc

3-8-2）使用$ne搜索不匹配的数据

for doc in collection.find({"Status":{"$ne":"In use"}}):
doc

3-8-3）使用$in搜索不匹配的数据

for doc in collection.find({"Tags":{"$in":["Not used","Development"]}},{"ItemNumber": True}).limit(2)

doc

3-8-4）使用$nin指定不匹配的数组

for doc in collection.find({"Tags":{"$nin":["Development"]}},{"ItemNumber":True}):

doc

3-8-5）搜索匹配数组值的文档

for doc in collection.find({"Tags":{"$all":["Storage","Not used"]}},{"ItemNumber":True}):

doc

3-8-6）使用$or指定多个匹配表达式
for doc in collection.find({"$or":[{"Location.Department":"Storage"},{"Location.Owner":"Anderson, Thomas"}]}):

doc

3-8-7）使用$slice从数组中获取元素

重新输入一组数据

chair = ({
"Status":"Not used",
"Tags":["Chair","Not used","Storage"],
"ItemNumber":"6789SID",
"Location":{
"Department":"Storage",
"Building":"2B"
},
"PreviousLocation":["120100","120101","120102","120103","120104","120105","120106","120107","120108","120109","120110"]
})

collection.insert_one(chair)

collection.find_one({'ItemNumber':'6789SID'},{'PreviousLocation':{'$slice':3}})

collection.find_one({'ItemNumber':'6789SID'},{'PreviousLocation':{'$slice':-3}})

 collection.find_one({'ItemNumber':'6789SID'},{'PreviousLocation':{'$slice':[5,3]}})

3-8-9）使用正则表达式执行搜索

import re

for doc in collection.find({'ItemNumber':re.compile('4')},{'ItemNumber':True}):
doc

for doc in collection.find({'ItemNumber':re.compile('.FS$')},{'ItemNumber':True}):
doc

for doc in collection.find({'Location.Owner':re.compile('^anderson.',re.IGNORECASE)},{'ItemNumber':True,'Location.Owner':True}):
doc

3-9）修改数据

3-9-1）更新数据

update = ({
"Type":"Chair",
"Status":"Not used",
"Tags":["Chair","Not used","Storage"],
"ItemNumber":"6789SID",
"Location":{
"Department":"Storage",
"Building":"2B",
"DeskNumber":131131,
"Owner":"Martin, Lisa"
}
})

collection.update_one({"ItenNumber":"6789SID"},update)

3-9-2）修改操作符

使用$inc增加整数值：

collection.update_one({"ItemNumber":"6789SID"},{"$inc":{"Location.DeskNumber":20}})

使用$set修改现有值：

collection.update_many({"Location.Department":"Development"},{"$set":{"Location.Building":"3B"}})

使用$unset移除键/值字段：

collection.update_one({"Status":"Not used","ItemNumber":"2345FDX"},{"$unset":{"Location.Building":1}})

使用$push向数组中添加值

collection.update_many({"Location.Owner":"Anderson, Thomas"},{"$push":{"Tags":"Anderson"}})

使用$push和$each向数组中添加多个值

collection.update_one({"Location.Owner":re.compile("^Walker,")},{"$push":{'Tags':{'$each':['Walker','Warranty']}}})

使用$addToSet向现有数组中添加值

 collection.update_many({"Type":"Chair"},{"$addToSet":{"Tags":"Warranty"}})

使用$pop从数组中删除元素

删除第一个元素

collection.update_one({"type":"Chair"},{"$pop":{"Tags":-1}})

删除最后一个元素

collection.update_one({"type":"Chair"},{"$pop":{"Tags":1}})

使用$pull删除特定的值（全部删除）

collection.update_one({"type":"Chair"},{"$pull":{"Tags":"Double"}})

使用replace_one()代替文档

collection.repalce_one(Desktop, NewDocument, upsert=True)

4）批处理数据

bulk = collection.initialize_ordered_bulk_op()

bulk.insert({"Type":"Laptop","ItemNumber":"2345EXD","Status":"Available"})

5）删除数据

删除文档

collection.delete_one({"Status":"In use"})

删除集合

db.items.drop()

删除数据库

c.drop_datebase("library")

6）在两个文档之间建立链接

在PyMongo中，数据库引用(DBRef)是通过DBRef模块中的DBRef()函数实现的，它可在处于不同位置的两个文档之间创建链接。

jan = {
"First Name" : "Jan",
"Last Name" : "Walker",
"Display name" : "Walker, Jan",
"Department" : "Development",
"Building" : "2B",
"Floor" : 12,
"Desk" : 120103,
"E-mail" : "jw@example.com"
}

people = db.people

people.insert(jan)

laptop = {
"Type" : "Laptop",
"Status" : "In use",
"ItemNumber" : "12345ABC",
"Tags" : ["Warranty","In use","Laptop"],
"Owner" : jan["_id"]
}

items = db.items

items.insert_one(laptop)

from bson.dbref import DBRef

mike = {
"First name" : "Mike",
"Last name" : "Wazowski",
"Display name" : "Wazowski, Mike",
"Department" : "Entertainment",
"Building" : "2B",
"Floor" : 10,
"Desk" : 120789,
"E-Mail" : "mw@monsters.inc"
}

people.insert_one(mike)

laptop = {
"Type" : "Laptop",
"Status" : "In use",
"ItemNumber" : "2345DEF",
"Tags" : ["Warranty","In use","Laptop"],
"Owner" : DBRef('people',mike["_id"])
}

items.insert_one(laptop)

person = items.find_one({"ItemNumber":"2345DEF"})

db.dereference(person["Owner"])