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Python Anslut till MySQL-databas med MySQL Connector &PyMySQL-exempel

När du vill ansluta till MySQL-databasen i Python-kod kan du använda både mysql-connector-python MySQL-drivrutin och PyMySQL . Den mysql-connector-python MySQL-drivrutinen är en MySQL-server inbyggd drivrutin och PyMySQL är ett tredjepartsbibliotek.

Alla de två MySQL pythonbiblioteken tillhandahåller klasser för dig att få MySQL-databasanslutning, exekvera infoga, ta bort, uppdatera, välj SQL-kommando. De stöder också transaktionshantering. Den här artikeln visar ett exempel på hur du använder mysql-connector-python och PyMySQL att arbeta på MySQL-databastabellen.

1. Hur man använder mysql-connector-python för att driva MySQL-databasen.

1.1 Installera mysql-connector-python Library.

  1. mysql-connector-python biblioteket kan installeras när du installerar MySQL-databasen.
  2. Så du kan köra kommandot pip show mysql-connector-python för att kontrollera om den har installerats eller inte.
    $ pip show mysql-connector-python
WARNING: Package(s) not found: mysql-connector-python
  3. Om mysql-connector-python biblioteket inte är installerat kan du köra kommandot pip install mysql-connector-python för att installera det.
    $ pip install mysql-connector-python
Collecting mysql-connector-python
  Downloading mysql_connector_python-8.0.25-py2.py3-none-any.whl (319 kB)
     |████████████████████████████████| 319 kB 219 kB/s 
Collecting protobuf>=3.0.0
  Downloading protobuf-3.17.0-cp37-cp37m-macosx_10_9_x86_64.whl (959 kB)
     |████████████████████████████████| 959 kB 727 kB/s 
Requirement already satisfied: six>=1.9 in /Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages (from protobuf>=3.0.0->mysql-connector-python) (1.15.0)
Installing collected packages: protobuf, mysql-connector-python
Successfully installed mysql-connector-python-8.0.25 protobuf-3.17.0
  4. När du nu kör kommandot pip show mysql-connector-python igen, du kan få dess installationsinformation.
    $ pip show mysql-connector-python
Name: mysql-connector-python
Version: 8.0.25
Summary: MySQL driver written in Python
Home-page: http://dev.mysql.com/doc/connector-python/en/index.html
Author: Oracle and/or its affiliates
Author-email: UNKNOWN
License: GNU GPLv2 (with FOSS License Exception)
Location: /Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages
Requires: protobuf
Required-by:

1.2 Använd mysql-connector-python Anslut till MySQL-databas Steg.

  1. Importera mysql.connector class.
    import mysql.connector
  2. Anropa mysql.connector.connect() metod för att ansluta till MySQL databasserver.
    # get mysql connection object.
def open_mysql_connection(user='jerry', password='jerry', host='127.0.0.1', port='3306', database='dev2qa_example', use_unicode=True):
    conn = mysql.connector.connect(user=user, password=password, host=host, port=port, database=database, use_unicode=use_unicode)
    return conn

1.3 Kör DDL-satsen för att skapa en tabell.

  1. Hämta MySQL-databasmarkören.
    cursor = conn.cursor()
  2. Kör DDL-satsen. Om du vill köra flera DDL-satser samtidigt måste du separera varje DDL-sats med semikolon, och du bör lägga till multi=True
    parameter till markörobjektets execute() metod, annars kommer felet mysql.connector.errors.InterfaceError:Använd multi=True när du kör flera satser . 

    def execute_ddl(conn):
    cursor = conn.cursor()
    
    # The below DDL will first drop the table if exist, then create the table.
    ddl_sql= '''
    
       DROP TABLE user_account;
    
       CREATE TABLE `dev2qa_example`.`user_account` (
      `id` INT NOT NULL AUTO_INCREMENT,
      `user_name` VARCHAR(45) NULL,
      `password` VARCHAR(45) NULL,
      `email` VARCHAR(45) NULL,
      PRIMARY KEY (`id`));
       '''
    # Because the above DDL contains 2 statements ( drop, create), so need to add the multi=True parameter to avoid error mysql.connector.errors.InterfaceError: Use multi=True when executing multiple statements.
    cursor.execute(ddl_sql, multi=True)
    cursor.close()
    
    conn.close()
    
    print(ddl_sql + ' execute successfully.')

1.4 Kör DML-utlåtande ( Infoga, Uppdatera, Ta bort ).

  1. Hämta MySQL-databasanslutningsmarkörobjekt.
  2. Kör insert, update, delete SQL-satsen med markörobjektets execute() metod.
    def execute_dml(conn):
    
    cursor = conn.cursor()
    
    dml_insert = ''' INSERT INTO `dev2qa_example`.`user_account` VALUES (null, %s, %s, %s); ''' 
    
    cursor.execute(dml_insert, ('tom', 'tom12345678', '[email protected]'))
    
    conn.commit()
    
    cursor.close()
    
    conn.close()
  3. Om du vill infoga flera rader i MySQL-tabellen kan du köra markörobjektets executemany() metod.
    def execute_dml_insert_many(conn):
    
    cursor = conn.cursor()
    
    dml_insert = ''' INSERT INTO `dev2qa_example`.`user_account` VALUES (null, %s, %s, %s); ''' 
    
    row_tuple = (('richard', 'richard', '[email protected]'), ('trump', 'trump', '[email protected]'),('doctor', 'doctor', '[email protected]'))
    
    cursor.executemany(dml_insert, row_tuple)
    
    conn.commit()
    
    cursor.close()
    
    conn.close()

1.5 Kör DML Välj SQL-sats.

  1. Kör markörobjektets execute() metod för att köra vald SQL-sats.
    def execute_dml_select(conn):
    
    cursor = conn.cursor()
    
    dml_select = 'SELECT * FROM dev2qa_example.user_account;'
    
    cursor.execute(dml_select)
    
    # print the row header.
    for col in cursor.description:
        
        print(col[0], end='\t')
        
        
    print('\n-----------------------------') 
    
    # print each row data.
    for row in cursor:
        
        print(row)   
        
        print(row[1] + '--->' + row[2])
           
        
    cursor.close()
    
    conn.close()

2. Hur man använder PtMySQL för att driva MySQL-databasen.

2.1 Installera PyMySQL.

  1. Innan du kan använda PyMySQL bör du installera det först. Du kan använda pip för att installera som nedan.
    $ pip3 install PyMySQL
  2. Du kan köra pip3 show kommando för att verifiera PyMySQL-installationen.
    $ pip3 show PyMySQL

2.2 Använd PyMySQL för att ansluta och driva MySQL-databasen.

Nedan är stegen som du använder PyMySQL-biblioteket i Python-kod.

  1. Importera PyMSQL connect , markörer class.
    from pymysql import connect, cursors
  2. Ring anslut metod för att hämta MySQL-databasanslutningsobjekt.
    conn = connect(host=host, user=user, password=password, db=db, charset=charset, cursorclass=cursorclass)
  3. Hämta databasmarkörobjekt genom anslutningsobjektets cursor()-funktion.
    conn.cursor() as cursor:
  4. Kör SQL-satsen med markörobjektet.
    cursor.execute(sql)
  5. Om sql-satsen är en select-sats, anropa markörobjektets fetchall()- eller fetchone()-metod för att få sql-exekveringsresultatet. Observera att efter att ha anropat fetchall(), kommer markören att flyttas till den sista raden i resultatet, så om du anropar fetchall()-metoden igen kommer ingen rad att returneras.
    row = cursor.fetchall()

or

row = cursor.fetchone()
  6. Om sql-satsen är en insert, update, delete-sats, anropa anslutningsobjektets commit()-funktion för att överföra ändringarna till MySQL-databasen för att träda i kraft.
    conn.commit()
  7. Glöm inte att stänga MySQL-databasanslutningsobjektet i slutet för att frigöra databasresurser.
    if conn is not None:
        conn.close()
        conn = None

2.3 PyMySQL Operate MySQL Database Exempel.

  1. I det här exemplet är MySQL-databasens namn dev2qa_example , tabellnamnet är användarkonto . Tabellen har fyra kolumner som är id , användarnamn , lösenord, och e-post . Id-kolumnen ökas automatiskt.
  2. Python-källkoden innehåller metoder för att infoga, uppdatera, ta bort och välja användarkontodata som nedan.
    from pymysql import connect, cursors

global_host='127.0.0.1'
global_user='jerry'
global_password='jerry'
global_db='dev2qa_example'
global_charset='utf8'
global_cursorclass=cursors.DictCursor

# get mysql connection object.
def open_mysql_connection(host='127.0.0.1', user='jerry', password='jerry', db='dev2qa_example', charset='utf8', cursorclass=cursors.DictCursor):
    conn = connect(host=host, user=user, password=password, db=db, charset=charset, cursorclass=cursorclass)
    return conn
    
# close mysql connection.    
def close_mysql_connection(conn):
    if conn is not None:
        conn.close()
        conn = None

# execute insert, update or delete sql command.
def execute_insert_update_delete_sql(sql, host, user, password, db, charset, cursorclass):
    execute_row_count = 0
    conn = None
    print('sql = ' + sql)
    try:
        if string_is_not_empty(sql):
            conn = open_mysql_connection(host, user, password, db, charset, cursorclass)
            with conn.cursor() as cursor:
                execute_row_count = cursor.execute(sql)
    except Exception as ex:
        print(ex)
    finally:
        if conn is not None:
            conn.commit()
            close_mysql_connection(conn)
        return execute_row_count    
 
# execute select sql command.                    
def execute_select_sql(sql, host, user, password, db, charset, cursorclass):
    ret = list()
    conn = None
    print('sql = ' + sql)
    try:
        if string_is_not_empty(sql):
            conn = open_mysql_connection(host, user, password, db, charset, cursorclass)
            with conn.cursor() as cursor:
                row_count = cursor.execute(sql)
                print('select return row count = ' + str(row_count))
                row = cursor.fetchall()
                print(row)
                ret.append(row)
    except Exception as ex:
        print(ex)            
    finally:
        if conn is not None:
            close_mysql_connection(conn)
        return ret        

# insert user account to database table dev2qa_example.user_account.                
def insert_user_account(user_name, password, email):
    print('**********Begin insert_user_account.**********')
    
    if string_is_not_empty(user_name) and string_is_not_empty(password) and string_is_not_empty(email):
        # first check whether user account exist or not.
        sql = "select count(id) as count from dev2qa_example.user_account where lower(user_name) = '"+user_name.lower().strip()+"'"
        row_list = execute_select_sql(sql, global_host, global_user, global_password, global_db, global_charset, global_cursorclass)
        
        account_exist = False
        for row in row_list:
            for column in row:
                exist_count_number = column.get('count')
                if exist_count_number > 0:
                    account_exist = True
        
        if not account_exist:
            print('User ' + user_name + ' do not exist in database. Insert the user account to database table.')
            sql = "insert into user_account(user_name, password, email) values('"+user_name+"','"+password+"','"+email+"')"
            insert_row_count = execute_insert_update_delete_sql(sql, global_host, global_user, global_password, global_db, global_charset, global_cursorclass)
            print('Insert ' + str(insert_row_count) + ' row data successfully.')
        else:
            print('User account exist, can not insert.')    
    else:
        print('user_name, password, email can not be empty.')        
        
    print('**********End insert_user_account.**********')    
   
# update user account data.            
def update_user_account(user_name, password, email):
    print('**********Begin update_user_account.**********')
    
    if string_is_not_empty(user_name):
        sql = "update dev2qa_example.user_account set password = '" + password + "', email = '" + email + "' where lower(user_name) = '" + user_name.lower() + "'"
        update_row_count = execute_insert_update_delete_sql(sql, global_host, global_user, global_password, global_db, global_charset, global_cursorclass)
    
        if update_row_count == 0:
            print('User account do not exist, insert it now.')
            insert_user_account(user_name, password, email)
        else:
            print('Update ' + str(update_row_count) + ' row data successfully.')
    else:
        print('user_name can not be empty.')        
           
    print('**********End update_user_account.**********')
    
# delete user account data from database table.    
def delete_user_account(user_name):
    print('**********Begin delete_user_account.**********')
    
    if string_is_not_empty(user_name):
        sql = "delete from dev2qa_example.user_account where lower(user_name) = '"+user_name.lower()+"'"
        delete_row_count = execute_insert_update_delete_sql(sql, global_host, global_user, global_password, global_db, global_charset, global_cursorclass)
        print('Delete ' + str(delete_row_count) + ' row data successfully.')
        
    print('**********End delete_user_account.**********')
    
# execute select sql command to get user account data by user_name.    
def get_user_account_by_user_name(user_name):
    print('**********Begin get_user_account_by_user_name.**********')
    sql = "select * from dev2qa_example.user_account where lower(user_name) = '"+user_name.lower().strip()+"'"
    row_list = execute_select_sql(sql, global_host, global_user, global_password, global_db, global_charset, global_cursorclass)
    print('**********End get_user_account_by_user_name.**********')

# check whether the string is empty or not.
def string_is_not_empty(str):
    if str is None:
        return False
    elif len(str.strip()) == 0:
        return False
    else:
        return True

if __name__ == '__main__':
    # first delete user account jerry.
    delete_user_account('jerry')
    
    # then insert a user account jerry into database.
    insert_user_account('jerry', 'jerry', '[email protected]')
    # show user account data to verify the insert action.
    get_user_account_by_user_name('jerry')
    
    # update usr account information.
    update_user_account('jerry', 'jerry888', '[email protected]')
    # check the updated user account info again.
    get_user_account_by_user_name('jerry')
  3. Nedan är resultatet av kodexekveringen ovan.
    **********Begin delete_user_account.**********
sql = delete from dev2qa_example.user_account where lower(user_name) = 'jerry'
Delete 1 row data successfully.
**********End delete_user_account.**********
**********Begin insert_user_account.**********
sql = select count(id) as count from dev2qa_example.user_account where lower(user_name) = 'jerry'
select return row count = 1
[{'count': 0}]
User jerry do not exist in database. Insert the user account to database table.
sql = insert into user_account(user_name, password, email) values('jerry','jerry','[email protected]')
Insert 1 row data successfully.
**********End insert_user_account.**********
**********Begin get_user_account_by_user_name.**********
sql = select * from dev2qa_example.user_account where lower(user_name) = 'jerry'
select return row count = 1
[{'id': 42, 'user_name': 'jerry', 'password': 'jerry', 'email': '[email protected]'}]
**********End get_user_account_by_user_name.**********
**********Begin update_user_account.**********
sql = update dev2qa_example.user_account set password = 'jerry888', email = '[email protected]' where lower(user_name) = 'jerry'
Update 1 row data successfully.
**********End update_user_account.**********
**********Begin get_user_account_by_user_name.**********
sql = select * from dev2qa_example.user_account where lower(user_name) = 'jerry'
select return row count = 1
[{'id': 42, 'user_name': 'jerry', 'password': 'jerry888', 'email': '[email protected]'}]
**********End get_user_account_by_user_name.**********

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