Python轻量级ORM框架Peewee访问sqlite数据库的方法详解

c:\Python27\Scripts>pip install peewee
Collecting peewee
 Downloading peewee-2.8.5.tar.gz (506kB)
  100% |████████████████████████████████| 512kB 437kB/s
Installing collected packages: peewee
 Running setup.py install for peewee ... done
Successfully installed peewee-2.8.5

# -*- coding:utf8 -*-
from peewee import *
db = SqliteDatabase('test.db')
class BaseModel(Model):
  class Meta:
    database = db
class Course(BaseModel):
  id = PrimaryKeyField()
  title = CharField(null = False)
  period = IntegerField()
  description = CharField()
  class Meta:
    order_by = ('title',)
    db_table = 'course'
class Teacher(BaseModel):
  id = PrimaryKeyField()
  name = CharField(null = False)
  gender = BooleanField()
  address = CharField()
  course_id = ForeignKeyField(Course,to_field='id',related_name = "course")
  class Meta:
    order_by = ('name',)
    db_table = 'teacher'

# -*- coding:utf8 -*-
from orm import *
Course.create_table()
Teacher.create_table()
Course.create(id = 1,title='经济学',period = 320,description='文科必修')
Course.create(id = 2,title='大学语文',period = 300,description='所有学科必修')
Course.create(id = 3,title='操作系统',period = 320,description='计算机必修')
Course.create(id = 4,title='马克思主义哲学',period = 320,description='必修')
Teacher.create(id = 1,name = '张三',gender=True,address='...',course_id = 1)
Teacher.create(id = 2,name = '李四',gender=False,address='-',course_id = 2)
Teacher.create(id = 3,name = '王五',gender=True,address='=',course_id = 3)

# -*- coding:gbk -*-
from orm import *
#获取1行数据
record = Course.get(Course.title=='大学语文')
print("课程：%s ,学时: %d" %(record.title,record.period))
#更新这行数据的period字段，保存
record.period = 200
record.save()
print("学分改为:%d" % record.period)
#获取1行数据，再删除,如果不存在，则会报错
record = Course.get(Course.title=='马克思主义哲学')
record.delete_instance()
###查询所有数据
course = Course.select()
###查询符合条件的数据，排序
course = Course.select().where(Course.id <3).order_by(Course.period.desc())
###计算平均值
total = Course.select(fn.Avg(Course.period)).alias('avg_period')
###更新数据
Course.update(period=300).where(Course.id>2).execute()
###关联数据
Record = Course.select().join(Teacher).where(Teacher.gender == True)