python连接数据库出现pymysql pymysql.err.OperationalError 1045 Access denied错误的解决办法

import pymysql

conn = pymysql.connect(host='localhost',
                       port=3306,
                       user='root',
                       password='root',
                       database='test',
                       charset='utf8')
cursor = conn.cursor()

sql = 'show databases;'
res = cursor.execute(sql)
print(cursor.fetchall())

执行这段代码出错 ： pymysql.err.OperationalError: (1045, u"Access denied for user 'root'@'localhost' (using password: No)")

新版mysql使用的caching_sha2_password认证方式，换成mysql_native_password就可以。

步骤是在cmd命令行连接mysql, 

然后输入ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY 'root';