Connect to TiDB with SQLAlchemy

TiDB is a MySQL-compatible database, and SQLAlchemy is a popular Python SQL toolkit and Object Relational Mapper (ORM).

In this tutorial, you can learn how to use TiDB and SQLAlchemy to accomplish the following tasks:

• Set up your environment.
• Connect to your TiDB cluster using SQLAlchemy.
• Build and run your application. Optionally, you can find sample code snippets for basic CRUD operations.

Prerequisites

To complete this tutorial, you need:

• Python 3.8 or higher.
• Git.
• A TiDB cluster.

If you don't have a TiDB cluster, you can create one as follows:

• (Recommended) Follow Creating a TiDB Cloud Serverless cluster to create your own TiDB Cloud cluster.
• Follow Deploy a local test TiDB cluster or Deploy a production TiDB cluster to create a local cluster.

Run the sample app to connect to TiDB

This section demonstrates how to run the sample application code and connect to TiDB.

Step 1: Clone the sample app repository

Run the following commands in your terminal window to clone the sample code repository:

git clone https://github.com/tidb-samples/tidb-python-sqlalchemy-quickstart.git
cd tidb-python-sqlalchemy-quickstart

Step 2: Install dependencies

Run the following command to install the required packages (including SQLAlchemy and PyMySQL) for the sample app:

pip install -r requirements.txt

Why use PyMySQL?

SQLAlchemy is an ORM library that works with multiple databases. It provides a high-level abstraction of the database, which helps developers write SQL statements in a more object-oriented way. However, SQLAlchemy does not include a database driver. To connect to a database, you need to install a database driver. This sample application uses PyMySQL as the database driver, which is a pure Python MySQL client library that is compatible with TiDB and can be installed on all platforms.

You can also use other database drivers, such as mysqlclient and mysql-connector-python. But they are not pure Python libraries and require the corresponding C/C++ compiler and MySQL client for compiling. For more information, refer to SQLAlchemy official documentation.

Step 3: Configure connection information

Connect to your TiDB cluster depending on the TiDB deployment option you've selected.

• TiDB Cloud Serverless
• TiDB Cloud Dedicated
• TiDB Self-Managed

Step 4: Run the code and check the result

1. Execute the following command to run the sample code:

   python sqlalchemy_example.py
   

2. Check the Expected-Output.txt to see if the output matches.

Sample code snippets

You can refer to the following sample code snippets to complete your own application development.

For complete sample code and how to run it, check out the tidb-samples/tidb-python-sqlalchemy-quickstart repository.

Connect to TiDB

from sqlalchemy import create_engine, URL
from sqlalchemy.orm import sessionmaker

def get_db_engine():
    connect_args = {}
    if ${ca_path}:
        connect_args = {
            "ssl_verify_cert": True,
            "ssl_verify_identity": True,
            "ssl_ca": ${ca_path},
        }
    return create_engine(
        URL.create(
            drivername="mysql+pymysql",
            username=${tidb_user},
            password=${tidb_password},
            host=${tidb_host},
            port=${tidb_port},
            database=${tidb_db_name},
        ),
        connect_args=connect_args,
    )

engine = get_db_engine()
Session = sessionmaker(bind=engine)

When using this function, you need to replace ${tidb_host}, ${tidb_port}, ${tidb_user}, ${tidb_password}, ${tidb_db_name} and ${ca_path} with the actual values of your TiDB cluster.

Define a table

from sqlalchemy import Column, Integer, String
from sqlalchemy.orm import declarative_base

Base = declarative_base()

class Player(Base):
    id = Column(Integer, primary_key=True)
    name = Column(String(32), unique=True)
    coins = Column(Integer)
    goods = Column(Integer)

    __tablename__ = "players"

For more information, refer to SQLAlchemy documentation: Mapping classes with declarative.

Insert data

with Session() as session:
    player = Player(name="test", coins=100, goods=100)
    session.add(player)
    session.commit()

For more information, refer to Insert data.

Query data

with Session() as session:
    player = session.query(Player).filter_by(name == "test").one()
    print(player)

For more information, refer to Query data.

Update data

with Session() as session:
    player = session.query(Player).filter_by(name == "test").one()
    player.coins = 200
    session.commit()

For more information, refer to Update data.

Delete data

with Session() as session:
    player = session.query(Player).filter_by(name == "test").one()
    session.delete(player)
    session.commit()

For more information, refer to Delete data.

Next steps

• Learn more usage of SQLAlchemy from the documentation of SQLAlchemy.
• Learn the best practices for TiDB application development with the chapters in the Developer guide, such as Insert data, Update data, Delete data, Single table reading, Transactions, and SQL performance optimization.
• Learn through the professional TiDB developer courses and earn TiDB certifications after passing the exam.

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