Peewee 简明教程

Peewee - Model

Peewee API 中 Model 子类的一个对象对应一个表，该表位于已建立其连接的数据库中。它允许执行数据库表操作，通过 Model 类中定义的方法来实现。

An object of Model sub class in Peewee API corresponds to a table in the database with which connection has been established. It allows performing database table operations with the help of methods defined in the Model class.

一个用户定义的 Model 有一个或更多类属性，它们中的每一个都是 Field 类的对象。Peewee 有多个子类用于保存不同类型的数据。示例有 TextField、DatetimeField 等。它们对应于数据库表中的字段或列。关联的数据库和表以及模型配置的引用在 Meta 类中提及。以下属性用于指定配置 −

A user defined Model has one or more class attributes, each of them is an object of Field class. Peewee has a number of subclasses for holding data of different types. Examples are TextField, DatetimeField, etc. They correspond to the fields or columns in the database table. Reference of associated database and table and model configuration is mentioned in Meta class. Following attributes are used to specify configuration −

Meta class Attributes

下面解释了元类属性：

The meta class attributes are explained below −

Sr.No	Attribute & Description
1	Database Database for model.
2	db_table Name of the table to store data. By default, it is name of model class.
3	Indexes A list of fields to index.
4	primary_key A composite key instance.
5	Constraints A list of table constraints.
6	Schema The database schema for the model.
7	Temporary Indicate temporary table.
8	depends_on Indicate this table depends on another for creation.
9	without_rowid Indicate that table should not have rowid (SQLite only).

以下代码为 mydatabase.db 中的 User 表定义了 Model 类 -

Following code defines Model class for User table in mydatabase.db −

from peewee import *
db = SqliteDatabase('mydatabase.db')
class User (Model):
   name=TextField()
   age=IntegerField()
   class Meta:
      database=db
      db_table='User'
User.create_table()

create_table() 方法是 Model 类的一个类方法，它执行等效的 CREATE TABLE 查询。另一个实例方法 save() 添加了一个与对象对应行。

The create_table() method is a classmethod of Model class that performs equivalent CREATE TABLE query. Another instance method save() adds a row corresponding to object.

from peewee import *
db = SqliteDatabase('mydatabase.db')
class User (Model):
   name=TextField()
   age=IntegerField()
   class Meta:
      database=db
      db_table='User'

User.create_table()
rec1=User(name="Rajesh", age=21)
rec1.save()

Methods in Model class

Model 类中的其他方法如下所示 −

Other methods in Model class are as follows −

Sr.No	Model Class & Description
1	Classmethod alias() Create an alias to the model-class. It allows the same Model to any referred multiple times in a query.
2	Classmethod select() Performs a SELECT query operation. If no fields are explicitly provided as argument, the query will by default SELECT * equivalent.
3	Classmethod update() Performs an UPDATE query function.
4	classmethod insert() Inserts a new row in the underlying table mapped to model.
5	classmethod delete() Executes delete query and is usually associated with a filter by where clause.
6	classmethod get() Retrieve a single row from mapped table matching the given filters.
7	get_id() Instance method returns primary key of a row.
8	save() Save the data of object as a new row. If primary-key value is already present, it will cause an UPDATE query to be executed.
9	classmethod bind() Bind the model to the given database.