爬虫学习之-操作mysql

在操作数据库的时候，python2中一般使用mysqldb，但在python3中已经不在支持mysqldb了，我们可以用pymysql和mysql.connector。本文的所有操作都是在python3的pymysql下完成的。

一、基本操作

(1) 查询

import pymysql

conn = pymysql.connect(host='127.0.0.1', user='root', passwd='root', db='test')
cur = conn.cursor()

# 查询
sql = "select * from info"
reCount = cur.execute(sql)  # 返回受影响的行数
print(reCount)
data = cur.fetchall()  # 返回数据,返回的是tuple类型
print(data)
"""
((1, 'mj', 'tokyo'), (2, 'alex', 'newyork'), (3, 'tommy', 'beijing'))
"""

cur.close()
conn.close()

(2) 修改

import pymysql

conn = pymysql.connect(host='127.0.0.1', user='root', passwd='root', db='test')
cur = conn.cursor()

# 插入数据
sql2 = "insert into info(NAME,address ) VALUES(%s,%s)"  # sql语句，%s是占位符（%s是唯一的，不论什么数据类型都使用%s）用来防止sql注入
params = ('eric', 'wuhan')  # 参数
reCount = cur.execute(sql2, params)

# 批量插入
li = [('a1', 'b1'), ('a2', 'b2')]
sql3 = 'insert into info(NAME ,address) VALUES (%s,%s)'
reCount = cur.executemany(sql3, li)

conn.commit()  # 提交，执行多条命令只需要commit一次就行了

cur.close()
conn.close()

(3) 返回dict类型的数据

import pymysql

conn = pymysql.connect(host='127.0.0.1', user='root', passwd='root', db='test')
# cur = conn.cursor()
cur = conn.cursor(cursor=pymysql.cursors.DictCursor)    #创建cursor的时候，指定1其返回的cursor类型为dict

# 查询
sql = "select * from info"
reCount = cur.execute(sql)  # 返回受影响的行数
print(reCount)
data = cur.fetchall()  # 返回数据,返回的是tuple类型
print(data)

cur.close()
conn.close()

"""
[{'address': 'tokyo', 'name': 'mj', 'id': 1}, {'address': 'newyork', 'name': 'alex', 'id': 2}, {'address': 'beijing', 'name': 'tommy', 'id': 3}]
"""

(4)获取自增id

通过cur.lastrowid来获取自增id

# 插入数据
sql = "insert into info(NAME,address ) VALUES(%s,%s)"
params = ('eric', '/usr/bin/a.txt')
reCount = cur.execute(sql, params)
conn.commit()

new_id = cur.lastrowid  #获取自增id，提交完之后才能取到值
print(new_id)

二、cursor定位

使用fechone来逐条获取数据

data = cur.fetchone()
print(data)  

data = cur.fetchone()
print(data)  

data = cur.fetchone()
print(data)  

"""
(1, 'mj', 'tokyo')
(2, 'alex', 'newyork')
(3, 'tommy', 'beijing')
"""

(1) 绝对定位

cur.scroll(0,mode='absolute')

data = cur.fetchone()
print(data) 

cur.scroll(0,mode='absolute')

data = cur.fetchone()
print(data) 

data = cur.fetchone()
print(data)
"""
(1, 'mj', 'tokyo')
(1, 'mj', 'tokyo')
(2, 'alex', 'newyork')
"""

(2) 相对定位

cur.scroll(-1,mode='relative')

data = cur.fetchone()
print(data) 

data = cur.fetchone()
print(data)  

cur.scroll(-1,mode='relative')

data = cur.fetchone()
print(data)
"""
(1, 'mj', 'tokyo')
(2, 'alex', 'newyork')
(2, 'alex', 'newyork')
"""

三、解耦

这里简单实现一个用户登录的功能，以便对整个业务结构有一个整体的认识。

项目目录结构

index.py

#!/usr/bin/env python3
# -*- coding:utf-8 -*-

from model.admin import Admin

def main():
    usr = input("username:")
    pwd = input("password:")
    admin = Admin()
    result = admin.CheckValidate(usr, pwd)
    if not result:  # 一般会把简单的逻辑放在上面，复杂的逻辑放下面
        print("登录失败！")
    else:
        print("登陆成功！进入后台管理界面..")

if __name__ == "__main__":
    main()

admin.py

#!/usr/bin/env python3
# -*- coding:utf-8 -*-
from utility.sql_helper import MySqlHelper

class Admin():
    def __init__(self):
        self.__helper = MySqlHelper()

    def CheckValidate(self,username,password):
        sql = "select * from admin where username=%s and password=%s"
        params=(username,password)
        return self.__helper.getOne(sql,params)

sql_helper.py

#!/usr/bin/env python3
# -*- coding:utf-8 -*-
import pymysql
import conf

class MySqlHelper(object):
    def __init__(self):
        self.__conn_dict = conf.conn_dict  # 把数据库连接信心提取到conf中

    def getDict(self, sql, params):
        conn = pymysql.connect(**self.__conn_dict)
        cur = conn.cursor(cursor=pymysql.cursors.DictCursor)
        cur.execute(sql, params)
        data = cur.fetchall()
        cur.close()
        conn.close()
        return data

    def getOne(self, sql, params):
        conn = pymysql.connect(**self.__conn_dict)  # 加**后表示传入的是字典里的数据，否则报错
        cur = conn.cursor(cursor=pymysql.cursors.DictCursor)
        cur.execute(sql, params)
        data = cur.fetchone()
        cur.close()
        conn.close()
        return data

conf.py

#!/usr/bin/env python3
# -*- coding:utf-8 -*-

conn_dict = dict(host='127.0.0.1', user='root', passwd='root', db='test')