Details and examples of Python operations MySQL

  • 2020-05-30 20:30:39
  • OfStack

Python operation MySQL details and examples

There are three main libraries that use Python for MySQL, Python-MySQL (more familiar names may be MySQLdb), PyMySQL, and SQLAlchemy.

Python-MySQL has the oldest qualification, the core is built by C language, the interface is refined, and the performance is the best. The disadvantage is that the environment is more dependent, the installation is complex, and the update has been stopped in the past two years, only supporting Python2, not Python3.

PyMySQL is designed to replace Python-MySQL, pure python. The interface is compatible with Python-MySQL, easy to install, and supports Python3.

SQLAlchemy is an ORM framework, which does not provide low-level database operations, but relies on third party libraries such as MySQLdb and PyMySQL. Currently, SQLAlchemy is widely used in the programming field of Web.

This article focuses on the proper use of PyMySQL, with sample code selected from real-world projects.

The installation

The easy way:


pip install pymysql

Offline installation is required if networking is not available, for example:


pip install pymysql-x.x.x.tar.gz

The import


import pymysql

The connection


def connect_wxremit_db():
  return pymysql.connect(host='10.123.5.28',
              port=3306,
              user='root',
              password='root1234',
              database='db_name',
              charset='latin1')

The query


def query_country_name(cc2):
  sql_str = ("SELECT Fcountry_name_zh"
        + " FROM t_country_code"
        + " WHERE Fcountry_2code='%s'" % (cc2))
  logging.info(sql_str)

  con = mysql_api.connect_wxremit_db()
  cur = con.cursor()
  cur.execute(sql_str)
  rows = cur.fetchall()
  cur.close()
  con.close()

  assert len(rows) == 1, 'Fatal error: country_code does not exists!'
  return rows[0][0]

A simple insert


def insert_file_rec(self, file_name, file_md5):
    con = mysql_api.connect_wxremit_db()
    cur = con.cursor()
    try:
      sql_str = ("INSERT INTO t_forward_file (Ffile_name, Ffile_md5)", 
            + " VALUES ('%s', '%s')" % (file_name, file_md5))
      cur.execute(sql_str)
      con.commit()
    except:
      con.rollback()
      logging.exception('Insert operation error')
      raise
    finally:
      cur.close()
      con.close()

Bulk insert


remit_ids = [('1234', 'CAD'), ('5678', 'HKD')]

con = mysql_api.connect_wxremit_db()
    cur = con.cursor()
    try:
        cur.executemany("INSERT INTO t_order (Fremit_id, Fcur_type, Fcreate_time"
                        + " VALUES (%s, %s, now())", new_items)
        assert cur.rowcount == len(remit_ids), 'my error message'
        con.commit()
    except Exception as e:
        con.rollback()
        logging.exception('Insert operation error')
    finally:
        cur.close()
        con.close()

update


 def update_refund_trans(self, remit_id):
    con = mysql_api.connect_wxremit_db()
    cur = con.cursor()
    try:
      sql_str = ("SELECT Fremit_id"
            + " FROM t_wxrefund_trans"
            + " WHERE Fremit_id='%s'" % remit_id
            + " FOR UPDATE")
      logging.info(sql_str)

      cur.execute(sql_str)
      assert cur.rowcount == 1, 'Fatal error: The wx-refund record be deleted!'

      sql_str = ("UPDATE t_wxrefund_trans"
            + " SET Fcheck_amount_flag=1"
            + ", Fmodify_time=now()"
            + " WHERE Fremit_id='%s'" % remit_id
      logging.info(sql_str)
      cur.execute(sql_str)

      assert cur.rowcount == 1, 'The number of affected rows not equal to 1'
      con.commit()
    except:
      con.rollback()
      logging.exception('Update operation error')
      raise
    finally:
      cur.close()
      con.close()

PyMySQL is quite mature and, like Python-MySQL1, is an optional installation component in many Linux distributions.

Thank you for reading, I hope to help you, thank you for your support of this site!


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