5.1 Connecting to MySQL Using Connector/Python

The connect() constructor creates a connection to the MySQL server and returns a MySQLConnection object.

The following example shows how to connect to the MySQL server:

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import mysql.connector

cnx = mysql.connector.connect(user='scott', password='password',
                              host='127.0.0.1',
                              database='employees')
cnx.close()

Section 7.1, “Connector/Python Connection Arguments” describes the permitted connection arguments.

It is also possible to create connection objects using the connection.MySQLConnection() class:

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from mysql.connector import (connection)

cnx = connection.MySQLConnection(user='scott', password='password',
                                 host='127.0.0.1',
                                 database='employees')
cnx.close()

Both forms (either using the connect() constructor or the class directly) are valid and functionally equal, but using connect() is preferred and used by most examples in this manual.

To handle connection errors, use the try statement and catch all errors using the errors.Error exception:

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import mysql.connector
from mysql.connector import errorcode

try:
  cnx = mysql.connector.connect(user='scott',
                                database='employ')
except mysql.connector.Error as err:
  if err.errno == errorcode.ER_ACCESS_DENIED_ERROR:
    print("Something is wrong with your user name or password")
  elif err.errno == errorcode.ER_BAD_DB_ERROR:
    print("Database does not exist")
  else:
    print(err)
else:
  cnx.close()

Defining connection arguments in a dictionary and using the ** operator is another option:

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import mysql.connector

config = {
  'user': 'scott',
  'password': 'password',
  'host': '127.0.0.1',
  'database': 'employees',
  'raise_on_warnings': True
}

cnx = mysql.connector.connect(**config)

cnx.close()

Defining Logger options, a reconnection routine, and defined as a connection method named connect_to_mysql:

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import logging
import time
import mysql.connector

# Set up logger
logger = logging.getLogger(__name__)
logger.setLevel(logging.INFO)
formatter = logging.Formatter("%(asctime)s - %(name)s - %(levelname)s - %(message)s")

# Log to console
handler = logging.StreamHandler()
handler.setFormatter(formatter)
logger.addHandler(handler)

# Also log to a file
file_handler = logging.FileHandler("cpy-errors.log")
file_handler.setFormatter(formatter)
logger.addHandler(file_handler) 

def connect_to_mysql(config, attempts=3, delay=2):
    attempt = 1
    # Implement a reconnection routine
    while attempt < attempts + 1:
        try:
            return mysql.connector.connect(**config)
        except (mysql.connector.Error, IOError) as err:
            if (attempts is attempt):
                # Attempts to reconnect failed; returning None
                logger.info("Failed to connect, exiting without a connection: %s", err)
                return None
            logger.info(
                "Connection failed: %s. Retrying (%d/%d)...",
                err,
                attempt,
                attempts-1,
            )
            # progressive reconnect delay
            time.sleep(delay ** attempt)
            attempt += 1
    return None

Connecting and using the Sakila database using the above routine, assuming it's defined in a file named myconnection.py:

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from myconnection import connect_to_mysql

config = {
    "host": "127.0.0.1",
    "user": "user",
    "password": "pass",
    "database": "sakila",
}

cnx = connect_to_mysql(config, attempts=3)

if cnx and cnx.is_connected():

    with cnx.cursor() as cursor:

        result = cursor.execute("SELECT * FROM actor LIMIT 5")

        rows = cursor.fetchall()

        for rows in rows:

            print(rows)

    cnx.close()

else:

    print("Could not connect")

Using the Connector/Python Python or C Extension

Connector/Python offers two implementations: a pure Python interface and a C extension that uses the MySQL C client library (see Chapter 8, The Connector/Python C Extension). This can be configured at runtime using the use_pure connection argument. It defaults to False as of MySQL 8, meaning the C extension is used. If the C extension is not available on the system then use_pure defaults to True. Setting use_pure=False causes the connection to use the C Extension if your Connector/Python installation includes it, while use_pure=True to False means the Python implementation is used if available.

Note

The use_pure option and C extension were added in Connector/Python 2.1.1.

The following example shows how to set use_pure to False.

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import mysql.connector

cnx = mysql.connector.connect(user='scott', password='password',
                              host='127.0.0.1',
                              database='employees',
                              use_pure=False)
cnx.close()

It is also possible to use the C Extension directly by importing the _mysql_connector module rather than the mysql.connector module. For more information, see Section 8.2, “The _mysql_connector C Extension Module”.