Context manager for Python's MySQLdb

Question

I am used to (spoiled by?) python\'s SQLite interface to deal with SQL databases. One nice feature in python\'s SQLite\'s API the \"context manager,\" i.e., python\'s

Answer 1

Previously, MySQLdb connections were context managers. As of this commit on 2018-12-04, however, MySQLdb connections are no longer context managers, and users must explicitly call conn.commit() or conn.rollback(), or write their own context manager, such as the one below.

---

You could use something like this:

import config
import MySQLdb
import MySQLdb.cursors as mc
import _mysql_exceptions
import contextlib
DictCursor = mc.DictCursor
SSCursor = mc.SSCursor
SSDictCursor = mc.SSDictCursor
Cursor = mc.Cursor

@contextlib.contextmanager
def connection(cursorclass=Cursor,
               host=config.HOST, user=config.USER,
               passwd=config.PASS, dbname=config.MYDB,
               driver=MySQLdb):
    connection = driver.connect(
            host=host, user=user, passwd=passwd, db=dbname,
            cursorclass=cursorclass)
    try:
        yield connection
    except Exception:
        connection.rollback()
        raise
    else:
        connection.commit()
    finally:
        connection.close()

@contextlib.contextmanager
def cursor(cursorclass=Cursor, host=config.HOST, user=config.USER,
           passwd=config.PASS, dbname=config.MYDB):
    with connection(cursorclass, host, user, passwd, dbname) as conn:
        cursor = conn.cursor()
        try:
            yield cursor
        finally:
            cursor.close()


with cursor(SSDictCursor) as cur:
    print(cur)
    connection = cur.connection
    print(connection)
    sql = 'select * from table'
    cur.execute(sql)
    for row in cur:
        print(row)

To use it you would place config.py in your PYTHONPATH and define the HOST, USER, PASS, MYDB variables there.

Answer 2

Think things have changed since this question was originally asked. Somewhat confusingly (from my point of view at least), for recent versions of MySQLdb, if you use a connection in a context you get a cursor (as per the oursql example), not something that closes automatically (as you would if you opened a file for instance).

Here's what I do:

from contextlib import closing
with closing(getConnection()) as conn: #ensure that the connection is closed
    with conn as cursor:               #cursor will now auto-commit
        cursor.execute('SELECT * FROM tablename')