Python MongoDB - 快速指南

Python MongoDB - 简介

Pymongo 是一个 Python 发行版，提供用于处理 MongoDB 的工具，它是从 Python 连接到 MongoDB 数据库的首选方式。

安装

要安装 pymongo，首先确保您已正确安装 python3（以及 PIP）和 MongoDB。然后执行以下命令。

C:\WINDOWS\system32>pip install pymongo
Collecting pymongo
Using cached https://files.pythonhosted.org/packages/cb/a6/b0ae3781b0ad75825e00e29dc5489b53512625e02328d73556e1ecdf12f8/pymongo-3.9.0-cp37-cp37m-win32.whl
Installing collected packages: pymongo
Successfully installed pymongo-3.9.0

验证

安装 pymongo 后，打开一个新的文本文档，将以下行粘贴到其中，并将其保存为 test.py。

import pymongo

如果您已正确安装 pymongo，如果按照以下所示执行 test.py，则不应该出现任何问题。

D:\Python_MongoDB>test.py
D:\Python_MongoDB>

Python MongoDB - 创建数据库

与其他数据库不同，MongoDB 没有提供单独的命令来创建数据库。

通常，use 命令用于选择/切换到特定的数据库。此命令首先验证我们指定的数据库是否存在，如果存在，则连接到它。如果我们使用 use 命令指定的数据库不存在，则会创建一个新的数据库。

因此，您可以使用 use 命令在 MongoDB 中创建数据库。

语法

use DATABASE 语句的基本语法如下：

use DATABASE_NAME

示例

以下命令创建一个名为 mydb 的数据库。

>use mydb
switched to db mydb

您可以使用 db 命令验证您的创建，这将显示当前数据库。

>db
mydb

使用 Python 创建数据库

要使用 pymongo 连接到 MongoDB，您需要导入并创建一个 MongoClient，然后您可以直接访问您需要在属性 passion 中创建的数据库。

示例

以下示例在 MangoDB 中创建一个数据库。

from pymongo import MongoClient

#Creating a pymongo client
client = MongoClient('localhost', 27017)

#Getting the database instance
db = client['mydb']
print("Database created........")

#Verification
print("List of databases after creating new one")
print(client.list_database_names())

输出

Database created........
List of databases after creating new one:
['admin', 'config', 'local', 'mydb']

您还可以在创建 MongoClient 时指定端口和主机名，并以字典样式访问数据库。

示例

from pymongo import MongoClient

#Creating a pymongo client
client = MongoClient('localhost', 27017)

#Getting the database instance
db = client['mydb']
print("Database created........")

输出

Database created........

Python MongoDB - 创建集合

MongoDB 中的集合保存一组文档，类似于关系数据库中的表。

您可以使用 createCollection() 方法创建集合。此方法接受一个表示要创建的集合名称的字符串值和一个可选参数 options。

使用它，您可以指定以下内容：

集合的大小。
带限制的集合中允许的最大数量的文档。
我们创建的集合是否应该是带限制的集合（固定大小的集合）。
我们创建的集合是否应该自动建立索引。

语法

以下是创建 MongoDB 集合的语法。

db.createCollection("CollectionName")

示例

以下方法创建一个名为 ExampleCollection 的集合。

> use mydb
switched to db mydb
> db.createCollection("ExampleCollection")
{ "ok" : 1 }
>

同样，以下是一个使用 createCollection() 方法的选项创建集合的查询。

>db.createCollection("mycol", { capped : true, autoIndexId : true, size :
6142800, max : 10000 } )
{ "ok" : 1 }
>

使用 Python 创建集合

以下 Python 示例连接到 MongoDB 中的数据库（mydb），并在其中创建一个集合。

示例

from pymongo import MongoClient

#Creating a pymongo client
client = MongoClient('localhost', 27017)

#Getting the database instance
db = client['mydb']

#Creating a collection
collection = db['example']
print("Collection created........")

输出

Collection created........

Python MongoDB - 插入文档

您可以使用 insert() 方法将文档存储到 MongoDB 中。此方法接受 JSON 文档作为参数。

语法

以下是 insert 方法的语法。

>db.COLLECTION_NAME.insert(DOCUMENT_NAME)

示例

> use mydb
switched to db mydb
> db.createCollection("sample")
{ "ok" : 1 }
> doc1 = {"name": "Ram", "age": "26", "city": "Hyderabad"}
{ "name" : "Ram", "age" : "26", "city" : "Hyderabad" }
> db.sample.insert(doc1)
WriteResult({ "nInserted" : 1 })
>

同样，您还可以使用 insert() 方法插入多个文档。

> use testDB
switched to db testDB
> db.createCollection("sample")
{ "ok" : 1 }
> data = [
   {"_id": "1001", "name": "Ram", "age": "26", "city": "Hyderabad"}, 
   {"_id": "1002", "name" : "Rahim", "age" : 27, "city" : "Bangalore" }, 
   {"_id": "1003", "name" : "Robert", "age" : 28, "city" : "Mumbai" }
]
[
   {"_id" : "1001", "name" : "Ram", "age" : "26", "city" : "Hyderabad"},
   {"_id" : "1002", "name" : "Rahim", "age" : 27, "city" : "Bangalore"},
   {"_id" : "1003", "name" : "Robert", "age" : 28, "city" : "Mumbai"}
]
> db.sample.insert(data)
BulkWriteResult({
   "writeErrors" : [ ],
   "writeConcernErrors" : [ ],
   "nInserted" : 3,
   "nUpserted" : 0,
   "nMatched" : 0,
   "nModified" : 0,
   "nRemoved" : 0,
   "upserted" : [ ]
})
>

使用 Python 创建集合

Pymongo 提供了一个名为 insert_one() 的方法来在 MangoDB 中插入文档。对于此方法，我们需要以字典格式传递文档。

示例

以下示例在名为 example 的集合中插入一个文档。

from pymongo import MongoClient

#Creating a pymongo client
client = MongoClient('localhost', 27017)

#Getting the database instance
db = client['mydb']

#Creating a collection
coll = db['example']

#Inserting document into a collection
doc1 = {"name": "Ram", "age": "26", "city": "Hyderabad"}
coll.insert_one(doc1)
print(coll.find_one())

输出

{'_id': ObjectId('5d63ad6ce043e2a93885858b'), 'name': 'Ram', 'age': '26', 'city': 'Hyderabad'}

要使用 pymongo 将多个文档插入 MongoDB，您需要调用 insert_many() 方法。

from pymongo import MongoClient

#Creating a pymongo client
client = MongoClient('localhost', 27017)

#Getting the database instance
db = client['mydb']

#Creating a collection
coll = db['example']

#Inserting document into a collection
data = [
   {"_id": "101", "name": "Ram", "age": "26", "city": "Hyderabad"},
   {"_id": "102", "name": "Rahim", "age": "27", "city": "Bangalore"},
   {"_id": "103", "name": "Robert", "age": "28", "city": "Mumbai"}
]
res = coll.insert_many(data)
print("Data inserted ......")
print(res.inserted_ids)

输出

Data inserted ......
['101', '102', '103']

Python MongoDB - 查找

您可以使用 find() 方法读取/检索 MongoDB 中存储的文档。此方法以非结构化的方式检索并显示 MongoDB 中的所有文档。

语法

以下是 find() 方法的语法。

>db.COLLECTION_NAME.find()

示例

假设我们已使用以下查询将 3 个文档插入名为 testDB 的数据库中的名为 sample 的集合中：

> use testDB
> db.createCollection("sample")
> data = [
   {"_id": "1001", "name": "Ram", "age": "26", "city": "Hyderabad"},
   {"_id": "1002", "name" : "Rahim", "age" : 27, "city" : "Bangalore" },
   {"_id": "1003", "name" : "Robert", "age" : 28, "city" : "Mumbai" }
]
> db.sample.insert(data)

您可以使用 find() 方法检索插入的文档，如下所示：

> use testDB
switched to db testDB
> db.sample.find()
{ "_id" : "1001", "name" : "Ram", "age" : "26", "city" : "Hyderabad" }
{ "_id" : "1002", "name" : "Rahim", "age" : 27, "city" : "Bangalore" }
{ "_id" : "1003", "name" : "Robert", "age" : 28, "city" : "Mumbai" }
>

您还可以使用 findOne() 方法检索集合中的第一个文档，如下所示：

> db.sample.findOne()
{ "_id" : "1001", "name" : "Ram", "age" : "26", "city" : "Hyderabad" }

使用 Python 检索数据 (find)

pymongo 的 find_One() 方法用于根据您的查询检索单个文档，如果没有任何匹配项，此方法将不返回任何内容，如果您不使用任何查询，它将返回集合的第一个文档。

当您只需要检索一个结果文档或确定您的查询仅返回一个文档时，此方法非常方便。

示例

以下 Python 示例检索集合的第一个文档：

from pymongo import MongoClient

#Creating a pymongo client
client = MongoClient('localhost', 27017)

#Getting the database instance
db = client['mydatabase']

#Creating a collection
coll = db['example']

#Inserting document into a collection
data = [
   {"_id": "101", "name": "Ram", "age": "26", "city": "Hyderabad"},
   {"_id": "102", "name": "Rahim", "age": "27", "city": "Bangalore"},
   {"_id": "103", "name": "Robert", "age": "28", "city": "Mumbai"}
]
res = coll.insert_many(data)
print("Data inserted ......")
print(res.inserted_ids)

#Retrieving the first record using the find_one() method
print("First record of the collection: ")
print(coll.find_one())

#Retrieving a record with is 103 using the find_one() method
print("Record whose id is 103: ")
print(coll.find_one({"_id": "103"}))

输出

Data inserted ......
['101', '102', '103']
First record of the collection:
{'_id': '101', 'name': 'Ram', 'age': '26', 'city': 'Hyderabad'}
Record whose id is 103:
{'_id': '103', 'name': 'Robert', 'age': '28', 'city': 'Mumbai'}

要在一个查询中获取多个文档（find 方法的单次调用），您可以使用 pymongo 的 find() 方法。如果没有传递任何查询，它将返回集合的所有文档，如果您已将查询传递给此方法，它将返回所有匹配的文档。

示例

#Getting the database instance
db = client['myDB']

#Creating a collection
coll = db['example']

#Inserting document into a collection
data = [
   {"_id": "101", "name": "Ram", "age": "26", "city": "Hyderabad"},
   {"_id": "102", "name": "Rahim", "age": "27", "city": "Bangalore"},
   {"_id": "103", "name": "Robert", "age": "28", "city": "Mumbai"}
]
res = coll.insert_many(data)
print("Data inserted ......")

#Retrieving all the records using the find() method
print("Records of the collection: ")
for doc1 in coll.find():
   print(doc1)

#Retrieving records with age greater than 26 using the find() method
print("Record whose age is more than 26: ")
for doc2 in coll.find({"age":{"$gt":"26"}}):
   print(doc2)

输出

Data inserted ......
Records of the collection:
{'_id': '101', 'name': 'Ram', 'age': '26', 'city': 'Hyderabad'}
{'_id': '102', 'name': 'Rahim', 'age': '27', 'city': 'Bangalore'}
{'_id': '103', 'name': 'Robert', 'age': '28', 'city': 'Mumbai'}
Record whose age is more than 26:
{'_id': '102', 'name': 'Rahim', 'age': '27', 'city': 'Bangalore'}
{'_id': '103', 'name': 'Robert', 'age': '28', 'city': 'Mumbai'}

Python MongoDB - 查询

在使用 find() 方法检索时，您可以使用查询对象过滤文档。您可以将指定所需文档条件的查询作为参数传递给此方法。

运算符

以下是 MongoDB 查询中使用的运算符列表。

操作	语法	示例
等于	{"key" : "value"}	db.mycol.find({"by":"tutorials point"})
小于	{"key" :{$lt:"value"}}	db.mycol.find({"likes":{$lt:50}})
小于等于	{"key" :{$lte:"value"}}	db.mycol.find({"likes":{$lte:50}})
大于	{"key" :{$gt:"value"}}	db.mycol.find({"likes":{$gt:50}})
大于等于	{"key" {$gte:"value"}}	db.mycol.find({"likes":{$gte:50}})
不等于	{"key":{$ne: "value"}}	db.mycol.find({"likes":{$ne:50}})

示例1

以下示例检索名称为 sarmista 的集合中的文档。

from pymongo import MongoClient

#Creating a pymongo client
client = MongoClient('localhost', 27017)

#Getting the database instance
db = client['sdsegf']

#Creating a collection
coll = db['example']

#Inserting document into a collection
data = [
   {"_id": "1001", "name": "Ram", "age": "26", "city": "Hyderabad"},
   {"_id": "1002", "name": "Rahim", "age": "27", "city": "Bangalore"},
   {"_id": "1003", "name": "Robert", "age": "28", "city": "Mumbai"},
   {"_id": "1004", "name": "Romeo", "age": "25", "city": "Pune"},
   {"_id": "1005", "name": "Sarmista", "age": "23", "city": "Delhi"},
   {"_id": "1006", "name": "Rasajna", "age": "26", "city": "Chennai"}
]
res = coll.insert_many(data)
print("Data inserted ......")

#Retrieving data
print("Documents in the collection: ")
for doc1 in coll.find({"name":"Sarmista"}):
   print(doc1)

输出

Data inserted ......
Documents in the collection:
{'_id': '1005', 'name': 'Sarmista', 'age': '23', 'city': 'Delhi'}

示例2

以下示例检索集合中年龄值大于 26 的文档。

from pymongo import MongoClient

#Creating a pymongo client
client = MongoClient('localhost', 27017)

#Getting the database instance
db = client['ghhj']

#Creating a collection
coll = db['example']

#Inserting document into a collection
data = [
   {"_id": "1001", "name": "Ram", "age": "26", "city": "Hyderabad"},
   {"_id": "1002", "name": "Rahim", "age": "27", "city": "Bangalore"},
   {"_id": "1003", "name": "Robert", "age": "28", "city": "Mumbai"},
   {"_id": "1004", "name": "Romeo", "age": "25", "city": "Pune"},
   {"_id": "1005", "name": "Sarmista", "age": "23", "city": "Delhi"},
   {"_id": "1006", "name": "Rasajna", "age": "26", "city": "Chennai"}
]
res = coll.insert_many(data)
print("Data inserted ......")

#Retrieving data
print("Documents in the collection: ")
for doc in coll.find({"age":{"$gt":"26"}}):
   print(doc)

输出

Data inserted ......
Documents in the collection:
{'_id': '1002', 'name': 'Rahim', 'age': '27', 'city': 'Bangalore'}
{'_id': '1003', 'name': 'Robert', 'age': '28', 'city': 'Mumbai'}

Python MongoDB - 排序

在检索集合内容时，您可以使用 sort() 方法对它们进行排序并按升序或降序排列。

对于此方法，您可以传递字段和排序顺序（1 或 -1）。其中，1 表示升序，-1 表示降序。

语法

以下是 sort() 方法的语法。

>db.COLLECTION_NAME.find().sort({KEY:1})

示例

假设我们已创建一个集合并向其中插入了 5 个文档，如下所示：

> use testDB
switched to db testDB
> db.createCollection("myColl")
{ "ok" : 1 }
> data = [
   ... {"_id": "1001", "name": "Ram", "age": "26", "city": "Hyderabad"},
   ... {"_id": "1002", "name": "Rahim", "age": 27, "city": "Bangalore"},
   ... {"_id": "1003", "name": "Robert", "age": 28, "city": "Mumbai"},
   ... {"_id": "1004", "name": "Romeo", "age": 25, "city": "Pune"},
   ... {"_id": "1005", "name": "Sarmista", "age": 23, "city": "Delhi"},
   ... {"_id": "1006", "name": "Rasajna", "age": 26, "city": "Chennai"}
]
> db.sample.insert(data)
BulkWriteResult({
   "writeErrors" : [ ],
   "writeConcernErrors" : [ ],
   "nInserted" : 6,
   "nUpserted" : 0,
   "nMatched" : 0,
   "nModified" : 0,
   "nRemoved" : 0,
   "upserted" : [ ]
})

以下行检索集合中的所有文档，这些文档根据年龄按升序排序。

> db.sample.find().sort({age:1})
{ "_id" : "1005", "name" : "Sarmista", "age" : 23, "city" : "Delhi" }
{ "_id" : "1004", "name" : "Romeo", "age" : 25, "city" : "Pune" }
{ "_id" : "1006", "name" : "Rasajna", "age" : 26, "city" : "Chennai" }
{ "_id" : "1002", "name" : "Rahim", "age" : 27, "city" : "Bangalore" }
{ "_id" : "1003", "name" : "Robert", "age" : 28, "city" : "Mumbai" }
{ "_id" : "1001", "name" : "Ram", "age" : "26", "city" : "Hyderabad" }

使用 Python 对文档进行排序

要按升序或降序对查询结果进行排序，pymongo 提供了 sort() 方法。为此方法传递一个数字值，表示您需要的结果中的文档数量。

默认情况下，此方法根据指定的字段按升序对文档进行排序。如果您需要按降序排序，请将 -1 与字段名称一起传递：

coll.find().sort("age",-1)

示例

以下示例检索集合中的所有文档，并根据年龄值按升序排列：

from pymongo import MongoClient

#Creating a pymongo client
client = MongoClient('localhost', 27017)

#Getting the database instance
db = client['b_mydb']

#Creating a collection
coll = db['myColl']

#Inserting document into a collection
data = [
   {"_id": "1001", "name": "Ram", "age": "26", "city": "Hyderabad"},
   {"_id": "1002", "name": "Rahim", "age": "27", "city": "Bangalore"},
   {"_id": "1003", "name": "Robert", "age": "28", "city": "Mumbai"},
   {"_id": "1004", "name": "Romeo", "age": 25, "city": "Pune"},
   {"_id": "1005", "name": "Sarmista", "age": 23, "city": "Delhi"},
   {"_id": "1006", "name": "Rasajna", "age": 26, "city": "Chennai"}
]
res = coll.insert_many(data)
print("Data inserted ......")

#Retrieving first 3 documents using the find() and limit() methods
print("List of documents (sorted in ascending order based on age): ")
for doc1 in coll.find().sort("age"):
   print(doc1)

输出

Data inserted ......
List of documents (sorted in ascending order based on age):
{'_id': '1005', 'name': 'Sarmista', 'age': 23, 'city': 'Delhi'}
{'_id': '1004', 'name': 'Romeo', 'age': 25, 'city': 'Pune'}
{'_id': '1006', 'name': 'Rasajna', 'age': 26, 'city': 'Chennai'}
{'_id': '1001', 'name': 'Ram', 'age': '26', 'city': 'Hyderabad'}
{'_id': '1002', 'name': 'Rahim', 'age': '27', 'city': 'Bangalore'}
{'_id': '1003', 'name': 'Robert', 'age': '28', 'city': 'Mumbai'}

Python MongoDB - 删除文档

您可以使用 MongoDB 的 remove() 方法删除集合中的文档。此方法接受两个可选参数：

删除条件，指定删除文档的条件。
仅一个，如果您将 true 或 1 作为第二个参数传递，则只会删除一个文档。

语法

以下是 remove() 方法的语法：

>db.COLLECTION_NAME.remove(DELLETION_CRITTERIA)

示例

假设我们已创建一个集合并向其中插入了 5 个文档，如下所示：

> use testDB
switched to db testDB
> db.createCollection("myColl")
{ "ok" : 1 }
> data = [
   ... {"_id": "1001", "name": "Ram", "age": "26", "city": "Hyderabad"},
   ... {"_id": "1002", "name": "Rahim", "age": 27, "city": "Bangalore"},
   ... {"_id": "1003", "name": "Robert", "age": 28, "city": "Mumbai"},
   ... {"_id": "1004", "name": "Romeo", "age": 25, "city": "Pune"},
   ... {"_id": "1005", "name": "Sarmista", "age": 23, "city": "Delhi"},
   ... {"_id": "1006", "name": "Rasajna", "age": 26, "city": "Chennai"}
]
> db.sample.insert(data)
BulkWriteResult({
   "writeErrors" : [ ],
   "writeConcernErrors" : [ ],
   "nInserted" : 6,
   "nUpserted" : 0,
   "nMatched" : 0,
   "nModified" : 0,
   "nRemoved" : 0,
   "upserted" : [ ]
})

以下查询删除名称值为 Sarmista 的集合中的文档。

> db.sample.remove({"name": "Sarmista"})
WriteResult({ "nRemoved" : 1 })
> db.sample.find()
{ "_id" : "1001", "name" : "Ram", "age" : "26", "city" : "Hyderabad" }
{ "_id" : "1002", "name" : "Rahim", "age" : 27, "city" : "Bangalore" }
{ "_id" : "1003", "name" : "Robert", "age" : 28, "city" : "Mumbai" }
{ "_id" : "1004", "name" : "Romeo", "age" : 25, "city" : "Pune" }
{ "_id" : "1006", "name" : "Rasajna", "age" : 26, "city" : "Chennai" }

如果您在不传递删除条件的情况下调用 remove() 方法，则集合中的所有文档都将被删除。

> db.sample.remove({})
WriteResult({ "nRemoved" : 5 })
> db.sample.find()

使用 Python 删除文档

要从 MangoDB 的集合中删除文档，您可以使用 delete_one() 和 delete_many() 方法从集合中删除文档。

这些方法接受一个查询对象，指定删除文档的条件。

detele_one() 方法删除单个文档（如果匹配）。如果没有指定查询，此方法将删除集合中的第一个文档。

示例

以下 Python 示例删除 id 值为 1006 的集合中的文档。

from pymongo import MongoClient

#Creating a pymongo client
client = MongoClient('localhost', 27017)

#Getting the database instance
db = client['lpaksgf']

#Creating a collection
coll = db['example']

#Inserting document into a collection
data = [
   {"_id": "1001", "name": "Ram", "age": "26", "city": "Hyderabad"},
   {"_id": "1002", "name": "Rahim", "age": "27", "city": "Bangalore"},
   {"_id": "1003", "name": "Robert", "age": "28", "city": "Mumbai"},
   {"_id": "1004", "name": "Romeo", "age": 25, "city": "Pune"},
   {"_id": "1005", "name": "Sarmista", "age": 23, "city": "Delhi"},
   {"_id": "1006", "name": "Rasajna", "age": 26, "city": "Chennai"}
]
res = coll.insert_many(data)
print("Data inserted ......")

#Deleting one document
coll.delete_one({"_id" : "1006"})

#Retrieving all the records using the find() method
print("Documents in the collection after update operation: ")
for doc2 in coll.find():
   print(doc2)

输出

Data inserted ......
Documents in the collection after update operation:
{'_id': '1001', 'name': 'Ram', 'age': '26', 'city': 'Hyderabad'}
{'_id': '1002', 'name': 'Rahim', 'age': '27', 'city': 'Bangalore'}
{'_id': '1003', 'name': 'Robert', 'age': '28', 'city': 'Mumbai'}
{'_id': '1004', 'name': 'Romeo', 'age': 25, 'city': 'Pune'}
{'_id': '1005', 'name': 'Sarmista', 'age': 23, 'city': 'Delhi'}

同样，pymongo 的 delete_many() 方法将删除满足指定条件的所有文档。

示例

以下示例删除集合中年龄值大于 26 的所有文档：

from pymongo import MongoClient

#Creating a pymongo client
client = MongoClient('localhost', 27017)

#Getting the database instance
db = client['sampleDB']

#Creating a collection
coll = db['example']

#Inserting document into a collection
data = [
   {"_id": "1001", "name": "Ram", "age": "26", "city": "Hyderabad"},
   {"_id": "1002", "name": "Rahim", "age": "27", "city": "Bangalore"},
   {"_id": "1003", "name": "Robert", "age": "28", "city": "Mumbai"},
   {"_id": "1004", "name": "Romeo", "age": "25", "city": "Pune"},
   {"_id": "1005", "name": "Sarmista", "age": "23", "city": "Delhi"},
   {"_id": "1006", "name": "Rasajna", "age": "26", "city": "Chennai"}
]
res = coll.insert_many(data)
print("Data inserted ......")

#Deleting multiple documents
coll.delete_many({"age":{"$gt":"26"}})

#Retrieving all the records using the find() method
print("Documents in the collection after update operation: ")
for doc2 in coll.find():
   print(doc2)

输出

Data inserted ......
Documents in the collection after update operation:
{'_id': '1001', 'name': 'Ram', 'age': '26', 'city': 'Hyderabad'}
{'_id': '1004', 'name': 'Romeo', 'age': '25', 'city': 'Pune'}
{'_id': '1005', 'name': 'Sarmista', 'age': '23', 'city': 'Delhi'}
{'_id': '1006', 'name': 'Rasajna', 'age': '26', 'city': 'Chennai'}

如果您在不传递任何查询的情况下调用 delete_many() 方法，则此方法将删除集合中的所有文档。

coll.delete_many({})

Python MongoDB - 删除集合

您可以使用 MongoDB 的 drop() 方法删除集合。

语法

以下是 drop() 方法的语法：

db.COLLECTION_NAME.drop()

示例

以下示例删除名称为 sample 的集合：

> show collections
myColl
sample
> db.sample.drop()
true
> show collections
myColl

使用 Python 删除集合

您可以通过调用 drop() 方法删除/删除当前数据库中的集合。

示例

from pymongo import MongoClient

#Creating a pymongo client
client = MongoClient('localhost', 27017)

#Getting the database instance
db = client['example2']

#Creating a collection
col1 = db['collection']
col1.insert_one({"name": "Ram", "age": "26", "city": "Hyderabad"})
col2 = db['coll']
col2.insert_one({"name": "Rahim", "age": "27", "city": "Bangalore"})
col3 = db['myColl']
col3.insert_one({"name": "Robert", "age": "28", "city": "Mumbai"})
col4 = db['data']
col4.insert_one({"name": "Romeo", "age": "25", "city": "Pune"})

#List of collections
print("List of collections:")
collections = db.list_collection_names()
for coll in collections:
   print(coll)

#Dropping a collection
col1.drop()
col4.drop()
print("List of collections after dropping two of them: ")

#List of collections
collections = db.list_collection_names()
for coll in collections:
   print(coll)

输出

List of collections:
coll
data
collection
myColl
List of collections after dropping two of them:
coll
myColl

Python MongoDB - 更新

您可以使用 update() 方法或 save() 方法更新现有文档的内容。

update 方法修改现有文档，而 save 方法用新文档替换现有文档。

语法

以下是 MangoDB 的 update() 和 save() 方法的语法：

>db.COLLECTION_NAME.update(SELECTION_CRITERIA, UPDATED_DATA)
Or,
db.COLLECTION_NAME.save({_id:ObjectId(),NEW_DATA})

示例

假设我们在数据库中创建了一个集合，并在其中插入了 3 条记录，如下所示：

> use testdatabase
switched to db testdatabase
> data = [
   ... {"_id": "1001", "name": "Ram", "age": "26", "city": "Hyderabad"},
   ... {"_id": "1002", "name" : "Rahim", "age" : 27, "city" : "Bangalore" },
   ... {"_id": "1003", "name" : "Robert", "age" : 28, "city" : "Mumbai" }
]
[
   {"_id" : "1001", "name" : "Ram", "age" : "26", "city" : "Hyderabad"},
   {"_id" : "1002", "name" : "Rahim", "age" : 27, "city" : "Bangalore"},
   {"_id" : "1003", "name" : "Robert", "age" : 28, "city" : "Mumbai"}
]
> db.createCollection("sample")
{ "ok" : 1 }
> db.sample.insert(data)

以下方法更新 id 为 1002 的文档的 city 值。

>db.sample.update({"_id":"1002"},{"$set":{"city":"Visakhapatnam"}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.sample.find()
{ "_id" : "1001", "name" : "Ram", "age" : "26", "city" : "Hyderabad" }
{ "_id" : "1002", "name" : "Rahim", "age" : 27, "city" : "Visakhapatnam" }
{ "_id" : "1003", "name" : "Robert", "age" : 28, "city" : "Mumbai" }

同样，您可以使用相同 id 保存新数据来替换文档。

> db.sample.save({ "_id" : "1001", "name" : "Ram", "age" : "26", "city" : "Vijayawada" })
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.sample.find()
{ "_id" : "1001", "name" : "Ram", "age" : "26", "city" : "Vijayawada" }
{ "_id" : "1002", "name" : "Rahim", "age" : 27, "city" : "Visakhapatnam" }
{ "_id" : "1003", "name" : "Robert", "age" : 28, "city" : "Mumbai" }

使用 python 更新文档

类似于检索单个文档的 find_one() 方法，pymongo 的 update_one() 方法更新单个文档。

此方法接受一个查询，指定要更新的文档和更新操作。

示例

以下 Python 示例更新集合中文档的 location 值。

from pymongo import MongoClient

#Creating a pymongo client
client = MongoClient('localhost', 27017)

#Getting the database instance
db = client['myDB']

#Creating a collection
coll = db['example']

#Inserting document into a collection
data = [
   {"_id": "101", "name": "Ram", "age": "26", "city": "Hyderabad"},
   {"_id": "102", "name": "Rahim", "age": "27", "city": "Bangalore"},
   {"_id": "103", "name": "Robert", "age": "28", "city": "Mumbai"}
]
res = coll.insert_many(data)
print("Data inserted ......")

#Retrieving all the records using the find() method
print("Documents in the collection: ")
for doc1 in coll.find():
   print(doc1)
coll.update_one({"_id":"102"},{"$set":{"city":"Visakhapatnam"}})

#Retrieving all the records using the find() method
print("Documents in the collection after update operation: ")
for doc2 in coll.find():
   print(doc2)

输出

Data inserted ......
Documents in the collection:
{'_id': '101', 'name': 'Ram', 'age': '26', 'city': 'Hyderabad'}
{'_id': '102', 'name': 'Rahim', 'age': '27', 'city': 'Bangalore'}
{'_id': '103', 'name': 'Robert', 'age': '28', 'city': 'Mumbai'}
Documents in the collection after update operation:
{'_id': '101', 'name': 'Ram', 'age': '26', 'city': 'Hyderabad'}
{'_id': '102', 'name': 'Rahim', 'age': '27', 'city': 'Visakhapatnam'}
{'_id': '103', 'name': 'Robert', 'age': '28', 'city': 'Mumbai'}

类似地，pymongo 的update_many() 方法更新满足指定条件的所有文档。

示例

以下示例更新集合中所有文档（空条件）的位置值：

from pymongo import MongoClient

#Creating a pymongo client
client = MongoClient('localhost', 27017)

#Getting the database instance
db = client['myDB']

#Creating a collection
coll = db['example']

#Inserting document into a collection
data = [
   {"_id": "101", "name": "Ram", "age": "26", "city": "Hyderabad"},
   {"_id": "102", "name": "Rahim", "age": "27", "city": "Bangalore"},
   {"_id": "103", "name": "Robert", "age": "28", "city": "Mumbai"}
]
res = coll.insert_many(data)
print("Data inserted ......")

#Retrieving all the records using the find() method
print("Documents in the collection: ")
for doc1 in coll.find():
   print(doc1)
coll.update_many({},{"$set":{"city":"Visakhapatnam"}})

#Retrieving all the records using the find() method
print("Documents in the collection after update operation: ")
for doc2 in coll.find():
   print(doc2)

输出

Data inserted ......
Documents in the collection:
{'_id': '101', 'name': 'Ram', 'age': '26', 'city': 'Hyderabad'}
{'_id': '102', 'name': 'Rahim', 'age': '27', 'city': 'Bangalore'}
{'_id': '103', 'name': 'Robert', 'age': '28', 'city': 'Mumbai'}
Documents in the collection after update operation:
{'_id': '101', 'name': 'Ram', 'age': '26', 'city': 'Visakhapatnam'}
{'_id': '102', 'name': 'Rahim', 'age': '27', 'city': 'Visakhapatnam'}
{'_id': '103', 'name': 'Robert', 'age': '28', 'city': 'Visakhapatnam'}

Python MongoDB - 限制

在检索集合内容时，您可以使用 limit() 方法限制结果中的文档数量。此方法接受一个数字值，表示您希望结果中包含的文档数量。

语法

以下是 limit() 方法的语法：

>db.COLLECTION_NAME.find().limit(NUMBER)

示例

假设我们已创建一个集合并向其中插入了 5 个文档，如下所示：

> use testDB
switched to db testDB
> db.createCollection("sample")
{ "ok" : 1 }
> data = [
   ... {"_id": "1001", "name": "Ram", "age": "26", "city": "Hyderabad"},
   ... {"_id": "1002", "name": "Rahim", "age": 27, "city": "Bangalore"},
   ... {"_id": "1003", "name": "Robert", "age": 28, "city": "Mumbai"},
   ... {"_id": "1004", "name": "Romeo", "age": 25, "city": "Pune"},
   ... {"_id": "1005", "name": "Sarmista", "age": 23, "city": "Delhi"},
   ... {"_id": "1006", "name": "Rasajna", "age": 26, "city": "Chennai"}
]
> db.sample.insert(data)
BulkWriteResult({
   "writeErrors" : [ ],
   "writeConcernErrors" : [ ],
   "nInserted" : 6,
   "nUpserted" : 0,
   "nMatched" : 0,
   "nModified" : 0,
   "nRemoved" : 0,
   "upserted" : [ ]
})

以下代码行检索集合中的前 3 个文档。

> db.sample.find().limit(3)
{ "_id" : "1001", "name" : "Ram", "age" : "26", "city" : "Hyderabad" }
{ "_id" : "1002", "name" : "Rahim", "age" : 27, "city" : "Bangalore" }
{ "_id" : "1003", "name" : "Robert", "age" : 28, "city" : "Mumbai" }

使用 Python 限制文档

为了将查询结果限制到特定数量的文档，pymongo 提供了limit() 方法。为此方法传递一个数字值，表示您需要结果中包含的文档数量。

示例

以下示例检索集合中的前三个文档。

from pymongo import MongoClient

#Creating a pymongo client
client = MongoClient('localhost', 27017)

#Getting the database instance
db = client['l']

#Creating a collection
coll = db['myColl']

#Inserting document into a collection
data = [
   {"_id": "1001", "name": "Ram", "age": "26", "city": "Hyderabad"},
   {"_id": "1002", "name": "Rahim", "age": "27", "city": "Bangalore"},
   {"_id": "1003", "name": "Robert", "age": "28", "city": "Mumbai"},
   {"_id": "1004", "name": "Romeo", "age": 25, "city": "Pune"},
   {"_id": "1005", "name": "Sarmista", "age": 23, "city": "Delhi"},
   {"_id": "1006", "name": "Rasajna", "age": 26, "city": "Chennai"}
]
res = coll.insert_many(data)
print("Data inserted ......")

#Retrieving first 3 documents using the find() and limit() methods
print("First 3 documents in the collection: ")
for doc1 in coll.find().limit(3):
   print(doc1)

输出

Data inserted ......
First 3 documents in the collection:
{'_id': '1001', 'name': 'Ram', 'age': '26', 'city': 'Hyderabad'}
{'_id': '1002', 'name': 'Rahim', 'age': '27', 'city': 'Bangalore'}
{'_id': '1003', 'name': 'Robert', 'age': '28', 'city': 'Mumbai'}

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