Python：Peewee实践记录

文档：http://docs.peewee-orm.com/

安装

$ pip install peewee

1

将已有数据表转为Model

# 导出数据表为Model $ python -m pwiz -e mysql -H localhost -p 3306 -u root -P -o -i -t user data > user.py

1

2

打印执行SQL

import logging # 打印日志 logger = logging.getLogger('peewee') logger.addHandler(logging.StreamHandler()) logger.setLevel(logging.DEBUG) logger.propagate = False # 不向上传播

1

2

3

4

5

6

7

8

modle和dict转换

from playhouse.shortcuts import model_to_dict, dict_to_model # 快捷方式类 class ShortcutModel(object): @classmethod def from_dict(cls, data, ignore_unknown=False): return dict_to_model(cls, data=data, ignore_unknown=ignore_unknown) def to_dict(self, recurse=True, backrefs=False, only=None, exclude=None, seen=None, extra_attrs=None, fields_from_query=None, max_depth=None, manytomany=False): return model_to_dict( self, recurse=recurse, backrefs=backrefs, only=only, exclude=exclude, seen=seen, extra_attrs=extra_attrs, fields_from_query=fields_from_query, max_depth=max_depth, manytomany=manytomany )

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

示例

class BaseModel(Model, ShortcutModel): class Meta: Database = db

1

2

3

外键关联操作

1、建表

from datetime import datetime from peewee import * db = SqliteDatabase('people.db') class BaseModel(Model): class Meta: database = db class Person(BaseModel): id = IntegerField(primary_key=True) name = CharField() birthday = DateField() class Meta: table_name = 'person' class Pet(BaseModel): id = IntegerField(primary_key=True) # 一对多: 一个Person -> 多个Pet owner = ForeignKeyField(Person, backref='pets') name = CharField() create_time = DateTimeField(default=datetime.now) update_time = DateTimeField(default=datetime.now) class Meta: table_name = 'pet' # 创建表 db.create_tables([Person, Pet])

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

2、初始化数据

def init_data(): person1 = Person.create(name='Tom', birthday='2020-01-01') Pet.create(owner=person1, name='Dog') Pet.create(owner=person1, name='Cat') person2 = Person.create(name='Jack', birthday='2020-01-02') Pet.create(owner=person2, name='Dog') Pet.create(owner=person2, name='Cat') init_data() """ sqlite> select * from person; id name birthday ---------- ---------- ---------- 1 Tom 2020-01-01 2 Jack 2020-01-02 sqlite> select * from pet; id owner_id name create_time update_time ---------- ---------- ---------- ------------------- ------------------- 1 1 Dog 2021-03-02 10:16:07 2021-03-02 10:16:07 2 1 Cat 2021-03-02 10:16:07 2021-03-02 10:16:07 3 2 Dog 2021-03-02 10:36:01 2021-03-02 10:36:01 4 2 Cat 2021-03-02 10:36:01 2021-03-02 10:36:01

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

3、N+1问题

3-1、一对多，取列表

for row in Person.select(): print(row.name) for pet in row.pets: print(pet.name) """ 取N+1次 : 先取一次person列表；然后一个Person对象，取一次pets列表 ('SELECT "t1"."id", "t1"."name", "t1"."birthday" FROM "person" AS "t1"', []) ('SELECT "t1"."id", "t1"."owner_id", "t1"."name", "t1"."create_time", "t1"."update_time" FROM "pet" AS "t1" WHERE ("t1"."owner_id" = ?)', [1]) ('SELECT "t1"."id", "t1"."owner_id", "t1"."name", "t1"."create_time", "t1"."update_time" FROM "pet" AS "t1" WHERE ("t1"."owner_id" = ?)', [2]) """ # 优化后方法 users = Person.select() pets = Pet.select() users_with_pets = prefetch(users, pets) for row in users_with_pets: print(row.name) for pet in row.pets: print(pet.name) """ 固定取两次：一次person列表；一次pet列表 ('SELECT "t1"."id", "t1"."owner_id", "t1"."name", "t1"."create_time", "t1"."update_time" FROM "pet" AS "t1" WHERE ("t1"."owner_id" IN (SELECT "t2"."id" FROM "person" AS "t2"))', []) ('SELECT "t1"."id", "t1"."name", "t1"."birthday" FROM "person" AS "t1"', []) """

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

3-2、一对一查询，取列表

pets = Pet.select() for pet in pets: print(pet.name, pet.owner.name) """ N+1次查询:首先取pet列表;逐个取pet对应的person ('SELECT "t1"."id", "t1"."owner_id", "t1"."name", "t1"."create_time", "t1"."update_time" FROM "pet" AS "t1"', []) ('SELECT "t1"."id", "t1"."name", "t1"."birthday" FROM "person" AS "t1" WHERE ("t1"."id" = ?) LIMIT ? OFFSET ?', [1, 1, 0]) ('SELECT "t1"."id", "t1"."name", "t1"."birthday" FROM "person" AS "t1" WHERE ("t1"."id" = ?) LIMIT ? OFFSET ?', [1, 1, 0]) ('SELECT "t1"."id", "t1"."name", "t1"."birthday" FROM "person" AS "t1" WHERE ("t1"."id" = ?) LIMIT ? OFFSET ?', [2, 1, 0]) ('SELECT "t1"."id", "t1"."name", "t1"."birthday" FROM "person" AS "t1" WHERE ("t1"."id" = ?) LIMIT ? OFFSET ?', [2, 1, 0]) """ # 优化方法 pets = Pet.select(Pet, Person).join(Person) for pet in pets: print(pet.name, pet.owner.name) """ 固定取1次 ('SELECT "t1"."id", "t1"."owner_id", "t1"."name", "t1"."create_time", "t1"."update_time", "t2"."id", "t2"."name", "t2"."birthday" FROM "pet" AS "t1" INNER JOIN "person" AS "t2" ON ("t1"."owner_id" = "t2"."id")', []) """

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

打印SQL执行耗时

from functools import wraps import time import logging from peewee import MySQLDatabase, SENTINEL, Model logger = logging.getLogger('peewee') # 计时器 def timer(func): @wraps(func) def wrapper(*args, **kwargs): start_time = time.time() ret = func(*args, **kwargs) end_time = time.time() logger.debug("time: %.2f s" % (end_time - start_time)) return ret return wrapper class CustomMySQLDatabase(MySQLDatabase): """ 打印sql执行时间 see: https://github.com/coleifer/peewee/issues/2370 """ @timer def execute_sql(self, sql, params=None, commit=SENTINEL): return super().execute_sql(sql, params, commit)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

支持原样查询返回dict字典对象

使用cator 模块

pip install cator

1

doc: https://github.com/mouday/cator

from peewee import MySQLDatabase from cator import DatabaseProxy db = MySQLDatabase(**config) db_proxy = DatabaseProxy(db)

1

2

3

4

5

6

单个模型数据转dict字典

from copy import deepcopy class BaseModel(Model): def to_dict(self): """model to dict""" return deepcopy(self.__data__) class Meta: database = db

1

2

3

4

5

6

7

8

9

10

文档：avoiding-the-n-1-problem

Python

版权声明：本文内容由网络用户投稿，版权归原作者所有，本站不拥有其著作权，亦不承担相应法律责任。如果您发现本站中有涉嫌抄袭或描述失实的内容，请联系我们jiasou666@gmail.com 处理，核实后本网站将在24小时内删除侵权内容。