Peewee 简明教程

Peewee - Defining Database Dynamically

如果你的数据库计划在运行时发生变化，请使用 DatabaseProxy 帮助程序更好地控制其初始化方式。DatabaseProxy 对象是一个占位符，数据库可以在运行时使用它进行选择。

If your database is scheduled to vary at run-time, use DatabaseProxy helper to have better control over how you initialise it. The DatabaseProxy object is a placeholder with the help of which database can be selected in run-time.

在以下示例中，将根据应用程序的配置设置选择合适的数据库。

In the following example, an appropriate database is selected depending on the application’s configuration setting.

from peewee import *
db_proxy = DatabaseProxy() # Create a proxy for our db.

class MyUser (Model):
   name=TextField()
   city=TextField(constraints=[SQL("DEFAULT 'Mumbai'")])
   age=IntegerField()
   class Meta:
      database=db_proxy
      db_table='MyUser'

# Based on configuration, use a different database.
if app.config['TESTING']:
   db = SqliteDatabase(':memory:')
elif app.config['DEBUG']:
   db = SqliteDatabase('mydatabase.db')
else:
   db = PostgresqlDatabase(
      'mydatabase', host='localhost', port=5432, user='postgres', password='postgres'
   )

# Configure our proxy to use the db we specified in config.
db_proxy.initialize(db)
db.connect()
db.create_tables([MyUser])

你还可以使用在数据库类和模型类中声明的 bind() 方法，在运行时将模型与任何数据库对象相关联。

You can also associate models to any database object during run-time using bind() method declared in both database class and model class.

以下示例在数据库类中使用 bind() 方法。

Following example uses bind() method in database class.

from peewee import *

class MyUser (Model):
   name=TextField()
   city=TextField(constraints=[SQL("DEFAULT 'Mumbai'")])
   age=IntegerField()

db = MySQLDatabase('mydatabase', host='localhost', port=3306, user='root', password='')
db.connect()
db.bind([MyUser])
db.create_tables([MyUser])

在 Model 类中也定义了 bind() 方法。

The same bind() method is also defined in Model class.

from peewee import *

class MyUser (Model):
   name=TextField()
   city=TextField(constraints=[SQL("DEFAULT 'Mumbai'")])
   age=IntegerField()

db = MySQLDatabase('mydatabase', host='localhost', port=3306, user='root', password='')
db.connect()
MyUser.bind(db)
db.create_tables([MyUser])