Python 操作 MongoDB 数据库
MongoDB是一个存储文档型的数据库(非关系型数据库)
利用pymongo连接MongoDB
import pymongo
client = pymongo.MongoClient(host='localhost', port=27017)
# 或 pymongo.MongoClient('mongodb://localhost:23017/')
# 默认端口为:27017
指定数据库
# 指定操作test数据库
db = client.test 或 db = client['test']
指定集合
# 指定一个集合要操作的集合students
collection = db.students 或 collection = db['students']
插入数据
插入单条数据
# 插入一条数据
insert_one()方法
import pymongo
# 连接MongoDB
client = pymongo.MongoClient(host='localhost', port=27017)
# 指定数据库
db = client.test
# 指定集合
collection = db.students
# 数据
student = {
'id': '20180001',
'name': 'Jordan',
'age': 20,
'gender': 'male'
}
# 利用insert_one()方法插入一条数据
result = collection.insert_one(student)
print(result)
# 运行输出:<pymongo.results.InsertOneResult object at 0x11089b448>
# 在MongoDB中,每条数据其实都有一个_id属性来唯一标识。如果没有显式指明该属性,MongoDB会自动产生一个ObjectId类型的_id属性。
# 使用 insert_one()和 insert_many()方法来分别插入单条记录和多条记录
插入多条数据
# 插入多条数据
insert_many()方法
import pymongo
client = pymongo.MongoClient(host='localhost', port=27017)
db = client.test
collection = db.students
student1 = {
'id': '20180002',
'name': 'Lee Hua',
'age': 20,
'gender': 'male'
}
student2 = {
'id': '20180003',
'name': 'Mike',
'age': 21,
'gender': 'male'
}
result = collection.insert_many([student1, student2])
print(result)
print(result.inserted_ids)
# 调用inserted_ids属性可以获取数据的_id列表
# 运行输出:
<pymongo.results.InsertManyResult object at 0x110826d88>
[ObjectId('5d28b293e834575faf929428'), ObjectId('5d28b293e834575faf929429')]
查询
查询一条数据
# 查询一条数据
find_one()
import pymongo
client = pymongo.MongoClient(host='localhost', port=27017)
db = client.test
collection = db.students
result = collection.find_one({'name': 'Lee Hua'})
print(result)
# 输出:
{'_id': ObjectId('5d28b293e834575faf929428'), 'id': '20180002', 'name': 'Lee Hua', 'age': 20, 'gender': 'male'}
查询多条数据
# 查询一条数据
find()
import pymongo
client = pymongo.MongoClient(host='localhost', port=27017)
db = client.test
collection = db.students
result = collection.find()
print(result)
for r in result:
print(r)
# find()方法返回一个迭代器,用for循环逐条输出
# 输出结果:
<pymongo.cursor.Cursor object at 0x10e0f7320>
{'_id': ObjectId('5d28ae0360105a198d9d501a'), 'id': '20180001', 'name': 'Jordan', 'age': 20, 'gender': 'male'}
{'_id': ObjectId('5d28ae2d8b3d004feb604874'), 'id': '20180001', 'name': 'Jordan', 'age': 20, 'gender': 'male'}
{'_id': ObjectId('5d28b293e834575faf929428'), 'id': '20180002', 'name': 'Lee Hua', 'age': 20, 'gender': 'male'}
{'_id': ObjectId('5d28b293e834575faf929429'), 'id': '20180003', 'name': 'Mike', 'age': 21, 'gender': 'male'}
可以在这两个方法里面添加条件,如:
find(
{
'name': {'$regex': '^M.*'}
}
)
这里查找的是以'M'开头的名字的那些数据,
$regex指定的是正则表达式,
^M.*是一条正则表达式
更多功能符号(如$regex)、数值比较符号的查看MongoDB官方文档:https://docs.mongodb.com/?searchProperty=manual
计数
import pymongo
client = pymongo.MongoClient(host='localhost', port=27017)
db = client.test
collection = db.students
count = collection.count_documents(
{
'id': {'$regex': '^(2018)'}
}
)
# 输出id为2018开头的数据的条数
print(count)
排序
import pymongo
client = pymongo.MongoClient(host='localhost', port=27017)
db = client.test
collection = db.students
result = collection.find().sort('id', pymongo.ASCENDING)
for r in result:
print(r)
# 以id升序输出所有的数据:
{'_id': ObjectId('5d28ae0360105a198d9d501a'), 'id': '20180001', 'name': 'Jordan', 'age': 20, 'gender': 'male'}
{'_id': ObjectId('5d28ae2d8b3d004feb604874'), 'id': '20180001', 'name': 'Jordan', 'age': 20, 'gender': 'male'}
{'_id': ObjectId('5d28b293e834575faf929428'), 'id': '20180002', 'name': 'Lee Hua', 'age': 20, 'gender': 'male'}
{'_id': ObjectId('5d28b293e834575faf929429'), 'id': '20180003', 'name': 'Mike', 'age': 21, 'gender': 'male'}
# sort()方法进行排序
# pymongo.ASCENDING指定升序
# pymongo.DESCENDING指定降序
偏移
skip() 方法
import pymongo
client = pymongo.MongoClient(host='localhost', port=27017)
db = client.test
collection = db.students
results = collection.find().sort('id', pymongo.DESCENDING).skip(1)
print(
[
result['id'] for result in results
]
)
# 输出:
['20180002', '20180001', '20180001']
# skip(1)表示偏移1,即忽略前面一个元素
limit()方法
import pymongo
client = pymongo.MongoClient(host='localhost', port=27017)
db = client.test
collection = db.students
results = collection.find().sort('id', pymongo.DESCENDING).skip(1).limit(2)
print(
[
result['id'] for result in results
]
)
# 输出:
['20180002', '20180001']
# limit(2) 即表示限制输出的数据条数为两条
注意:数据量很大时,不使用大的偏移量来查询数据。
更新
update_one()方法
import pymongo
client = pymongo.MongoClient(host='localhost', port=27017)
db = client['test']
collection = db['students']
# 查询条件:age >= 20
query_condition = {
'age': {'$gte': 20}
}
# 更新条件:数据的age加1
update_condition = {
'$inc': {'age': 1}
}
result = collection.update_one(query_condition, update_condition)
print(result)
print(result.matched_count, result.modified_count)
# 输出:
<pymongo.results.UpdateResult object at 0x110a11c88>
1 1
# 返回的结果是UpdateResul类型的
# 调用matched_count属性,获得匹配数据的条数
# 调用modified_count属性,获得影响数据的条数
# $gte : 大于等于
# $inc : 将字段递增指定的值
# updata_one()更新与筛选器匹配的单个文档
update_many()方法
import pymongo
client = pymongo.MongoClient(host='localhost', port=27017)
db = client['test']
collection = db['students']
query_condition = {
'age': {'$gte': 20}
}
update_condition = {
'$inc': {'age': 1}
}
result = collection.update_many(query_condition, update_condition)
print(result)
print(result.matched_count, result.modified_count)
# 输出:
<pymongo.results.UpdateResult object at 0x111c84448>
4 4
删除
delete_one() 方法
import pymongo
client = pymongo.MongoClient(host='localhost', port=27017)
db = client['test']
collection = db['students']
result = collection.delete_one({'age': 21})
print(result.deleted_count)
# delete_one()方法:删除第一条符合条件的数据
# delete_count属性:获取删除数据的条数
delete_many() 方法
import pymongo
client = pymongo.MongoClient(host='localhost', port=27017)
db = client['test']
collection = db['students']
result = collection.delete_many({'age': 21})
print(result.deleted_count)
# delete_many()方法:删除所有符合条件的数据
PyMongo的详细用法
官方文档:http://api.mongodb.com/python/current/api/pymongo/collection.html
本文来自博客园,作者:LeeHua,转载请注明原文链接:https://www.cnblogs.com/liyihua/p/11179084.html