Python实现mysql数据库更新表数据接口的功能

前言

昨天，因为项目需求要添加表的更新接口，来存储预测模型训练的数据，所以自己写了一段代码实现了该功能，在开始之前，给大家分享python 操作mysql数据库基础：

#coding=utf-8
import MySQLdb

conn= MySQLdb.connect(
    host='localhost',
    port = 3306,
    user='root',
    passwd='123456',
    db ='test',
    )
cur = conn.cursor()

#创建数据表
#cur.execute("create table student(id int ,name varchar(20),class varchar(30),age varchar(10))")

#插入一条数据
#cur.execute("insert into student values('2','Tom','3 year 2 class','9')")


#修改查询条件的数据
#cur.execute("update student set class='3 year 1 class' where name = 'Tom'")

#删除查询条件的数据
#cur.execute("delete from student where age='9'")

cur.close()
conn.commit()
conn.close()

>>> conn = MySQLdb.connect(host='localhost',port = 3306,user='root', passwd='123456',db ='test',)

Connect() 方法用于创建数据库的连接，里面可以指定参数：用户名，密码，主机等信息。

这只是连接到了数据库，要想操作数据库需要创建游标。

>>> cur = conn.cursor()

通过获取到的数据库连接conn下的cursor()方法来创建游标。

>>> cur.execute("create table student(id int ,name varchar(20),class varchar(30),age varchar(10))")

通过游标cur 操作execute()方法可以写入纯sql语句。通过execute()方法中写如sql语句来对数据进行操作。

>>>cur.close()

cur.close() 关闭游标

>>>conn.commit()

conn.commit()方法在提交事物，在向数据库插入一条数据时必须要有这个方法，否则数据不会被真正的插入。

>>>conn.close()

Conn.close()关闭数据库连接

下面开始本文的正文：

Python实现mysql更新表数据接口

示例代码

# -*- coding: utf-8 -*-
import pymysql
import settings

class mysql(object):
 def __init__(self):
  self.db = None

 def connect(self):

   self.db = pymysql.connect(host=settings.ip, port=settings.port, user=settings.mysql_user, passwd=settings.mysql_passwd, db=settings.database, )
  # print("connect is ok")
   # return 1
 def disconnect(self):
  self.db.close()
  # return -1

 def create_table(self, tablename, columns, spec='time'):
  """
  :param tablename:
  :param spec:
  :param columns: 列表[]
  :return:
  """

  type_data = ['int', 'double(10,3)']
  cursor = self.db.cursor()
  sql="create table %s("%(tablename,)
  sqls=[]
  for col in columns:
   #判断是否time_num
   if col==spec:
    sqls.append('%s %s primary key'%(col,type_data[0]))
   else:
    sqls.append('%s %s'%(col,type_data[1]))

  sqlStr = ','.join(sqls)
  sql+=sqlStr+')'
  try:
   cursor.execute(sql)
   print("Table %s is created"%tablename)
  except:
   self.db.rollback()

 def is_table_exist(self, tablename,dbname):
  cursor=self.db.cursor()
  sql="select table_name from information_schema.TABLES where table_schema='%s' and table_name = '%s'"%(dbname,tablename)
  #results="error:Thie table is not exit"
  try:
   cursor.execute(sql)

   results = cursor.fetchall() #接受全部返回行
  except:
   #不存在这张表返回错误提示
    raise Exception('This table does not exist')
  if not results:
    return None
  else :
   return results
 # print datas
 def insert_mysql_with_json(self, tablename, datas):
  """

  :param tablename:
  :param datas:字典{(key: value),.....}
  :return:
  """
  # keys = datas[0]
  keys = datas[0].keys()
  keys = str(tuple(keys))
  keys = ''.join(keys.split("'")) # 用' 隔开
  print(keys)
  ret = []
  for dt in datas:
   values = dt.values() ##  ‘str' object has no attribute#
   sql = "insert into %s" % tablename + keys
   sql = sql + " values" + str(tuple(values))
   ret.append(sql)
   # print("1")
  # print keys insert into %tablename dat[i] values str[i]

  self.insert_into_sql(ret)
  print("1")
 def insert_into_sql(self,sqls):
  cursor = self.db.cursor()
  for sql in sqls:
   # 执行sql语句
   try:
    cursor.execute(sql)
    self.db.commit()
    # print("insert %s" % sql, "success.")
   except:
    # Rollback in case there is any error
    self.db.rollback()
 #找列名
 def find_columns(self, tablename):
  sql = "select COLUMN_NAME from information_schema.columns where table_name='%s'" % tablename
  cursor = self.db.cursor()
  try:
   cursor.execute(sql)
   results = cursor.fetchall()
  except:
   raise Exception('hello')
  return tuple(map(lambda x: x[0], results))

 def find(self, tablename, start_time, end_time, fieldName=None):
  """
  :param tablename: test_scale1015
  :param fieldName: None or (columns1010, columns1011, columns1012, columns1013, time)
  :return:
  """
  cursor = self.db.cursor()
  sql = ''
  if fieldName==None:
   fieldName = self.find_columns(tablename)
   sql = "select * from %s where time between %s and %s" % (tablename, str(start_time), str(end_time))
   # print('None')
  else:
   fieldNameStr = ','.join(fieldName)
   sql = "select %s from %s where time between %s and %s" % (
   fieldNameStr, tablename, str(start_time), str(end_time))
   # print('sm')
  try:
   cursor.execute(sql)
   results = cursor.fetchall()
  except:
   raise Exception('hello')
  return fieldName, results,
 
 #样例 data = [{'time':123321,'predict':1.222},{'time':123322,'predict':1.223},{'time':123324,'predict':1.213}]
 def updata(self,datas, tablename):
  cursor = self.db.cursor()
  columns = []
  for data in datas:
   for i in data.keys():
    columns.append(i)
   # print(columns)
   break
   # columns_2=columns[:]
  db.connect()
  if db.is_table_exist(settings.tablename_2, settings.database):
    # exists
    # pass
    for col in columns:
     if col != 'time':
      sql = "alter table %s add column %s double(10,3);" % (settings.tablename_2, col)
      try:
       cursor.execute(sql)
       print("%s is altered ok" % (col))
      except:
       print("alter is failed")
     

    ret = []
    for i in datas:
     col = []
     for ii in i.keys():
      col.append(ii)
     #time = col[0] and predict = col[1]
     time_data = i[col[0]]
     predic_data = i[col[1]]
     sql = "update %s set %s='%s'where %s=%s"%(settings.tablename_2,col[1],predic_data,col[0],time_data)
     ret.append(sql)
    self.insert_into_sql(ret)

    # db.insert_mysql_with_json(tablename, datas)


  else:
    # no exists
    db.create_table(settings.tablename_2, columns)
    db.insert_mysql_with_json(settings.tablename_2, datas)

db = mysql()

其中update（）函数，是新添加的接口：

传入的data的样例 data = [{'time':123321,'predict':1.222},{'time':123322,'predict':1.223},{'time':123324,'predict':1.213}] 这样子的。

一个列表里有多个字典，每个字典有time和predict。如果需要存predict_2,predict_3的时候，则实现更新操作，否则，只进行创表和插入数据的操作~~~~~~

看起来是不是很简单~~~~~~

这个接口还没有进行优化等操作，很冗余~~~~

毕竟项目还在测试阶段，等先跑通了，在考虑优化吧~~~~~~

总结