Python 操作SQLite数据库详情

前言：

sqlite属于轻型数据库，遵守acid的关系型数据库管理系统，它包含在一个相对小的c库中。在很多嵌入式产品中使用了它，它占用资源非常的低，python 中默认继承了操作此款数据库的引擎 sqlite3 说是引擎不如说就是数据库的封装版，开发自用小程序的使用使用它真的大赞

一、简单操作sqlite数据库

简单操作sqlite数据库:创建 sqlite数据库是一个轻量级的数据库服务器,该模块默认集成在python中,开发小应用很不错.

import sqlite3

# 数据表的创建
conn = sqlite3.connect("data.db")
cursor = conn.cursor()
create = "create table persion(" \
         "id int auto_increment primary key," \
         "name char(20) not null," \
         "age int not null," \
         "msg text default null" \
         ")"
cursor.execute(create)        # 执行创建表操作

1、简单的插入语句的使用

insert = "insert into persion(id,name,age,msg) values(1,'lyshark',1,'hello lyshark');"
cursor.execute(insert)
insert = "insert into persion(id,name,age,msg) values(2,'guest',2,'hello guest');"
cursor.execute(insert)
insert = "insert into persion(id,name,age,msg) values(3,'admin',3,'hello admin');"
cursor.execute(insert)
insert = "insert into persion(id,name,age,msg) values(4,'wang',4,'hello wang');"
cursor.execute(insert)
insert = "insert into persion(id,name,age,msg) values(5,'sqlite',5,'hello sql');"
cursor.execute(insert)

data = [(6, '王舞',8, 'python'), (7, '曲奇',8,'python'), (9, 'c语言',9,'python')]
insert = "insert into persion(id,name,age,msg) values(?,?,?,?);"
cursor.executemany(insert,data)

2、简单的查询语句的使用

select = "select * from persion;"
cursor.execute(select)
#print(cursor.fetchall())   # 取出所有的数据

select = "select * from persion where name='lyshark';"
cursor.execute(select)
print(cursor.fetchall())   # 取出所有的数据

select = "select * from persion where id >=1 and id <=2;"
list = cursor.execute(select)
for i in list.fetchall():
    print("字段1：", i[0])
    print("字段2：", i[1])

二、更新数据与删除

update = "update persion set name='苍老师' where id=1;"
cursor.execute(update)

update = "update persion set name='苍老师' where id>=1 and id<=3;"
cursor.execute(update)

delete = "delete from persion where id=3;"
cursor.execute(delete)

select = "select * from persion;"
cursor.execute(select)
print(cursor.fetchall())   # 取出所有的数据

conn.commit()       # 事务提交，每执行一次数据库更改的操作，就执行提交
cursor.close()
conn.close()

三、实现用户名密码验证

当用户输入错误密码后,自动锁定该用户1分钟.

import sqlite3
import re,time

conn = sqlite3.connect("data.db")
cursor = conn.cursor()
"""create = "create table login(" \
         "username text not null," \
         "password text not null," \
         "time int default 0" \
          ")"
cursor.execute(create)
cursor.execute("insert into login(username,password) values('admin','123123');")
cursor.execute("insert into login(username,password) values('guest','123123');")
cursor.execute("insert into login(username,password) values('lyshark','1231');")
conn.commit()"""

while true:
    username = input("username:")  # 这个地方应该严谨验证,尽量不要让用户拼接sql语句
    password = input("passwor:")   # 此处为了方便不做任何验证(注意:永远不要相信用户的输入)
    sql = "select * from login where username='{}'".format(username)
    ret = cursor.execute(sql).fetchall()
    if len(ret) != 0:
        now_time = int(time.time())
        if ret[0][3] <= now_time:
            print("当前用户{}没有被限制,允许登录...".format(username))
            if ret[0][0] == username:
                if ret[0][1] == password:
                    print("用户 {} 登录成功...".format(username))
                else:
                    print("用户 {} 密码输入有误..".format(username))
                    times = int(time.time()) + 60
                    cursor.execute("update login set time={} where username='{}'".format(times,username))
                    conn.commit()
            else:
                print("用户名正确,但是密码错误了...")
        else:
            print("账户 {} 还在限制登陆阶段,请等待1分钟...".format(username))
    else:
        print("用户名输入错误")

四、sqlite检索时间记录

通过编写的timeindex函数检索一个指定范围时间戳中的数据.

import os,time,datetime
import sqlite3

"""
conn = sqlite3.connect("data.db")
cursor = conn.cursor()
create = "create table lyshark(" \
         "time int primary key," \
         "cpu int not null" \
         ")"
cursor.execute(create)
# 批量生成一堆数据,用于后期的测试.
for i in range(1,500):
    times = int(time.time())
    insert = "insert into lyshark(time,cpu) values({},{})".format(times,i)
    cursor.execute(insert)
    conn.commit()
    time.sleep(1)"""

# db = data.db 传入数据库名称
# table = 指定表lyshark名称
# start = 2019-12-12 14:28:00
# ends  = 2019-12-12 14:29:20
def timeindex(db,table,start,ends):
    start_time = int(time.mktime(time.strptime(start,"%y-%m-%d %h:%m:%s")))
    end_time = int(time.mktime(time.strptime(ends,"%y-%m-%d %h:%m:%s")))
    conn = sqlite3.connect(db)
    cursor = conn.cursor()
    select = "select * from {} where time >= {} and time <= {}".format(table,start_time,end_time)
    return cursor.execute(select).fetchall()

if __name__ == "__main__":
    temp = timeindex("data.db","lyshark","2019-12-12 14:28:00","2019-12-12 14:29:00")
    print(temp)

五、sqlite提取数据并绘图

通过使用matplotlib这个库函数,并提取出指定时间的数据记录,然后直接绘制曲线图.

import os,time,datetime
import sqlite3
import numpy as np
from matplotlib import pyplot as plt

def timeindex(db,table,start,ends):
    start_time = int(time.mktime(time.strptime(start,"%y-%m-%d %h:%m:%s")))
    end_time = int(time.mktime(time.strptime(ends,"%y-%m-%d %h:%m:%s")))
    conn = sqlite3.connect(db)
    cursor = conn.cursor()
    select = "select * from {} where time >= {} and time <= {}".format(table,start_time,end_time)
    return cursor.execute(select).fetchall()

def display():
    temp = timeindex("data.db","lyshark","2019-12-12 14:28:00","2019-12-12 14:29:00")
    list = []
    for i in range(0,len(temp)):
        list.append(temp[i][1])
    plt.title("cpu count")
    plt.plot(list, list)
    plt.show()
    
if __name__ == "__main__":
    display()

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