Detailed explanation of ORM framework Peewee in Python

Detailed explanation of ORM framework Peewee in Python

ORM (Object Relational Mapping) is a technology that maps objects to relational databases. This article will introduce Peewee, an ORM framework in Python. Peewee is a lightweight, easy-to-use, flexible ORM framework that supports multiple databases such as SQLite, MySQL, and PostgreSQL. This article will introduce the installation, basic usage, advanced usage and comparison of Peewee with other ORM frameworks.

1. Installing Peewee

Peewee can be installed through pip. Enter the following command in the terminal to install:

pip install peewee

2. Basic usage

(1) Database connection

Before using Peewee, you need to do it first Database Connectivity. The following code shows how to connect to a SQLite database through Peewee:

from peewee import *

db = SqliteDatabase('my_database.db')

Among them, my_database.db is the name of the SQLite database. If the database file does not exist, the file will be created in the current directory.

Peewee also supports MySQL, PostgreSQL and other databases. You only need to replace SqliteDatabase with the corresponding database. For example, the following code shows how to connect to a MySQL database through Peewee:

db = MySQLDatabase('my_database', user='my_user', password='my_password', host='my_host', port=3306)

(2) Define the model

Peewee uses models to describe tables in the database. Each model represents a table, and each attribute represents a field in the table. The following code defines a model User, which contains two fields: id and name:

class User(Model):
    id = AutoField(primary_key=True)
    name = CharField()

    class Meta:
        database = db

Among them, AutoField represents the auto-incrementing primary key, primary_key=True represents the field as the primary key, and CharField represents the string type.

(3) Create table

After defining the model, you need to create the corresponding table in the corresponding database. Peewee provides the create_table method to create a table. The code is as follows:

User.create_table()

(4) Insert data

Peewee provides the save method to insert data into the database. The following code inserts a piece of data:

user = User(name='张三')
user.save()

(5) Query data

Peewee provides get and select methods to query data. Among them, the get method is used to query a single piece of data, and the select method is used to query multiple pieces of data. The following code queries all users named Zhang San:

users = User.select().where(User.name == '张三')
for user in users:
    print(user.id, user.name)

3. Advanced usage

(1) Related query

Peewee supports foreign key associations Inquire. The following code defines a model Order, which contains three fields: id, user and product:

class Order(Model):
    id = AutoField(primary_key=True)
    user = ForeignKeyField(User, backref='orders')
    product = CharField()

    class Meta:
        database = db

Among them, ForeignKeyField represents the foreign key, and backref='orders' means that the user can be accessed through User.orders All orders.

You can perform related queries through the join method, as shown below:

orders = Order.select().join(User).where(User.name == '张三')
for order in orders:
    print(order.id, order.user.name, order.product)

(2) Transaction operation

Peewee supports transaction operations. Multiple operations on the database can be encapsulated in with db.atomic(). The code is as follows:

with db.atomic() as txn:
    user1 = User(name='张三')
    user1.save()
    user2 = User(name='李四')
    user2.save()
    for i in range(10):
        order = Order(user=user1, product='product_' + str(i))
        order.save()
        order = Order(user=user2, product='product_' + str(i))
        order.save()

4. Comparison with other ORM frameworks

With Django’s own Compared with the ORM framework, Peewee is more lightweight and more flexible to use. Compared with SQLAlchemy, Peewee's syntax is more concise and clear, and it also provides many convenient advanced usages.

In short, Peewee is a recommended Python ORM framework. Due to its flexibility and ease of use, it is also widely used in many projects.

The above is the detailed content of Detailed explanation of ORM framework Peewee in Python. For more information, please follow other related articles on the PHP Chinese website!