Basic module usage

The basic Psycopg usage is common to all the database adapters implementing the DB-API protocol. Other database adapters, such as the builtin sqlite3 or psycopg2, have roughly the same pattern of interaction.

Main objects in psycopg3

Here is an interactive session showing some of the basic commands:

import psycopg3

# Connect to an existing database
with psycopg3.connect("dbname=test user=postgres") as conn:

    # Open a cursor to perform database operations
    with conn.cursor() as cur:

        # Execute a command: this creates a new table
            CREATE TABLE test (
                id serial PRIMARY KEY,
                num integer,
                data text)

        # Pass data to fill a query placeholders and let Psycopg perform
        # the correct conversion (no SQL injections!)
            "INSERT INTO test (num, data) VALUES (%s, %s)",
            (100, "abc'def"))

        # Query the database and obtain data as Python objects.
        cur.execute("SELECT * FROM test")
        # will return (1, 100, "abc'def")

        # You can use `cur.fetchmany()`, `cur.fetchall()` to return a list
        # of several records, or even iterate on the cursor
        for record in cur:

        # Make the changes to the database persistent

In the example you can see some of the main objects and methods and how they relate to each other:

See also

A few important topics you will have to deal with are:

Connection context

psycopg3 Connection can be used as a context manager:

with psycopg3.connect() as conn:
    ... # use the connection

# the connection is now closed

When the block is exited, if there is a transaction open, it will be committed. If an exception is raised within the block the transaction is rolled back. In either case the connection is closed.

AsyncConnection can be also used as context manager, using async with, but be careful about its quirkiness: see with async connections for details.