python往mysql数据库中动态写入数据和更新插入数据

1. 连接mysql

import pymysql
db = pymysql.connect(host='localhost', user='root', password='123456', port=3306, db='spiders')
cursor = db.cursor()
sql = 'select * from students;'
cursor.execute(sql)
cursor.close()
db.close()

2. 多字段动态插入mysql数据库中

import pymysql
db = pymysql.connect(host='localhost',user='root', password='123456', port=3306, db='spiders')
data = {
    'id': '20180606',
    'name': 'Lily',
    'age': 20
}
table = 'students'
keys = ', '.join(data.keys())
values = ', '.join(['%s'] * len(data))
sql = 'INSERT INTO {table}({keys}) VALUES ({values})'.format(table=table, keys=keys, values=values)
try:
   cursor.execute(sql, tuple(data.values()))
   print('Successful')
   db.commit()
except:
   print('Failed')
   db.rollback()
cursor.close()
db.close()

3. 数据更新插入mysql数据库中

import pymysql
db = pymysql.connect(host='localhost',user='root', password='123456', port=3306, db='spiders')
data = {
    'id': '20180606',
    'name': 'Lily',
    'age': 25
}
table = 'students'
keys = ', '.join(data.keys())
values = ', '.join(['%s'] * len(data))
sql = 'INSERT INTO {table}({keys}) VALUES ({values}) ON DUPLICATE KEY UPDATE'.format(table=table, keys=keys, values=values)
update = ','.join([" {key} = (%s)".format(key=key) for key in data])
sql += update
try:
   cursor.execute(sql, tuple(data.values()))
   print('Successful')
   db.commit()
except:
   print('Failed')
   db.rollback()
cursor.close()
db.close()

execute（sql，args）方法注意事项：

1、execute方法中sql语句占位符是%s，与mysql中的？不同。

2、%s必须用括号包裹，如：

insert into teacher(name) values (%s) 正确
insert into teacher(name) values %s 报错