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Dialects

A dialect chooses SQL syntax and connects Pysely to a database driver. You provide the connection or pool; Pysely does not accept a URL directly.

Choose a database below. The install commands use main, matching these docs. Run connection setup containing await inside your application's async startup.

uv add "pysely[postgres] @ git+https://github.com/mylesmmurphy/pysely.git@main"

pip install "pysely[postgres] @ git+https://github.com/mylesmmurphy/pysely.git@main"

import asyncpg

from pysely import PostgresDialect


pool = await asyncpg.create_pool("postgresql://user:password@localhost/app")
dialect = PostgresDialect(pool=pool)

Pysely acquires a pool connection for each query or connection scope.

A factory can initialize the pool lazily:

async def create_pool():
    return await asyncpg.create_pool("postgresql://localhost/app")


dialect = PostgresDialect(pool=create_pool)

uv add "pysely[mysql] @ git+https://github.com/mylesmmurphy/pysely.git@main"

pip install "pysely[mysql] @ git+https://github.com/mylesmmurphy/pysely.git@main"

import asyncmy

from pysely import MysqlDialect


pool = await asyncmy.create_pool(
    host="127.0.0.1",
    user="app",
    password="secret",
    db="app",
    autocommit=True,
)
dialect = MysqlDialect(pool=pool)

Keep autocommit=True. Explicit Pysely transactions still commit or roll back as a unit.

uv add "pysely[sqlite] @ git+https://github.com/mylesmmurphy/pysely.git@main"

pip install "pysely[sqlite] @ git+https://github.com/mylesmmurphy/pysely.git@main"

import aiosqlite

from pysely import SqliteDialect


database = await aiosqlite.connect("app.db", isolation_level=None)
dialect = SqliteDialect(database=database)

isolation_level=None enables autocommit. Use ":memory:" instead of "app.db" for a temporary database.

Create and close the client

Use the dialect from the selected tab:

from dbschema import DatabaseSchema

async with DatabaseSchema.connect(dialect=dialect) as db:
    rows = await db.select_from("person").select("id").execute()

For a long-lived client, create it at startup and call await db.destroy() at shutdown.

Pysely closes the configured pool or connection. Do not give it a resource that another part of your application must keep using after the client is destroyed.

Database differences

Database Driver Important boundary
PostgreSQL asyncpg Connection pools supported
MySQL asyncmy No full join or returning() through this API
SQLite aiosqlite One configured connection
SQL Server / PGlite No runtime adapter yet Offline compilation only