Contents
13.2. Python 操作SQLite数据库¶
13.2.1. 连接数据库¶
下面的 Python 代码显示了如何连接到一个现有的数据库。如果数据库不存在，那么它就会被创建，最后将返回一个数据库对象。
#!/usr/bin/python
import sqlite3
conn = sqlite3.connect('test.db')
print "Opened database successfully";
在这里，您也可以把数据库名称复制为特定的名称 :memory:，这样就会在 RAM 中创建一个数据库。现在，让我们来运行上面的程序，在当前目录中创建我们的数据库 test.db。您可以根据需要改变路径。保存上面代码到 sqlite.py 文件中，并按如下所示执行。如果数据库成功创建，那么会显示下面所示的消息：
$chmod +x sqlite.py
$./sqlite.py
Open database successfully
13.2.2. 创建表¶
下面的 Python 代码段将用于在先前创建的数据库中创建一个表：
#!/usr/bin/python
import sqlite3
conn = sqlite3.connect('test.db')
print "Opened database successfully";
c = conn.cursor()
c.execute('''CREATE TABLE COMPANY
(ID INT PRIMARY KEY NOT NULL,
NAME TEXT NOT NULL,
AGE INT NOT NULL,
ADDRESS CHAR(50),
SALARY REAL);''')
print "Table created successfully";
conn.commit()
conn.close()
上述程序执行时，它会在 test.db 中创建 COMPANY 表，并显示下面所示的消息：
Opened database successfully
Table created successfully
13.2.3. INSERT 操作¶
下面的 Python 程序显示了如何在上面创建的 COMPANY 表中创建记录：
#!/usr/bin/python
import sqlite3
conn = sqlite3.connect('test.db')
c = conn.cursor()
print "Opened database successfully";
c.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
VALUES (1, 'Paul', 32, 'California', 20000.00 )");
c.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
VALUES (2, 'Allen', 25, 'Texas', 15000.00 )");
c.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
VALUES (3, 'Teddy', 23, 'Norway', 20000.00 )");
c.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
VALUES (4, 'Mark', 25, 'Rich-Mond ', 65000.00 )");
conn.commit()
print "Records created successfully";
conn.close()
上述程序执行时，它会在 COMPANY 表中创建给定记录，并会显示以下两行：
Opened database successfully
Records created successfully
13.2.4. SELECT 操作¶
下面的 Python 程序显示了如何从前面创建的 COMPANY 表中获取并显示记录：
#!/usr/bin/python
import sqlite3
conn = sqlite3.connect('test.db')
c = conn.cursor()
print "Opened database successfully";
cursor = c.execute("SELECT id, name, address, salary from COMPANY")
for row in cursor:
print "ID = ", row[0]
print "NAME = ", row[1]
print "ADDRESS = ", row[2]
print "SALARY = ", row[3], "\n"
print "Operation done successfully";
conn.close()
上述程序执行时，它会产生以下结果：
Opened database successfully
ID = 1
NAME = Paul
ADDRESS = California
SALARY = 20000.0
ID = 2
NAME = Allen
ADDRESS = Texas
SALARY = 15000.0
ID = 3
NAME = Teddy
ADDRESS = Norway
SALARY = 20000.0
ID = 4
NAME = Mark
ADDRESS = Rich-Mond
SALARY = 65000.0
Operation done successfully
13.2.5. UPDATE 操作¶
下面的 Python 代码显示了如何使用 UPDATE 语句来更新任何记录，然后从 COMPANY 表中获取并显示更新的记录：
#!/usr/bin/python
import sqlite3
conn = sqlite3.connect('test.db')
c = conn.cursor()
print "Opened database successfully";
c.execute("UPDATE COMPANY set SALARY = 25000.00 where ID=1")
conn.commit()
print "Total number of rows updated :", conn.total_changes
cursor = conn.execute("SELECT id, name, address, salary from COMPANY")
for row in cursor:
print "ID = ", row[0]
print "NAME = ", row[1]
print "ADDRESS = ", row[2]
print "SALARY = ", row[3], "\n"
print "Operation done successfully";
conn.close()
上述程序执行时，它会产生以下结果：
Opened database successfully
Total number of rows updated : 1
ID = 1
NAME = Paul
ADDRESS = California
SALARY = 25000.0
ID = 2
NAME = Allen
ADDRESS = Texas
SALARY = 15000.0
ID = 3
NAME = Teddy
ADDRESS = Norway
SALARY = 20000.0
ID = 4
NAME = Mark
ADDRESS = Rich-Mond
SALARY = 65000.0
Operation done successfully
13.2.6. DELETE 操作¶
下面的 Python 代码显示了如何使用 DELETE 语句删除任何记录，然后从 COMPANY 表中获取并显示剩余的记录：
#!/usr/bin/python
import sqlite3
conn = sqlite3.connect('test.db')
c = conn.cursor()
print "Opened database successfully";
c.execute("DELETE from COMPANY where ID=2;")
conn.commit()
print "Total number of rows deleted :", conn.total_changes
cursor = conn.execute("SELECT id, name, address, salary from COMPANY")
for row in cursor:
print "ID = ", row[0]
print "NAME = ", row[1]
print "ADDRESS = ", row[2]
print "SALARY = ", row[3], "\n"
print "Operation done successfully";
conn.close()
上述程序执行时，它会产生以下结果：
Opened database successfully
Total number of rows deleted : 1
ID = 1
NAME = Paul
ADDRESS = California
SALARY = 20000.0
ID = 3
NAME = Teddy
ADDRESS = Norway
SALARY = 20000.0
ID = 4
NAME = Mark
ADDRESS = Rich-Mond
SALARY = 65000.0
Operation done successfully
13.2.7. Pyhton操作SQLite数据库案例¶
#!/usr/bin/env python
# -*- coding:utf8 -*-
# auther; 18793
# Date：2019/6/24 17:02
# filename: SQLite3操作数据库.py
import sqlite3
import random
src = "abcdefghijklmnopqrstuvwxyz"
def get_str(x, y):
""" 生成随机数，x~y之间的随机字母字符串"""
str_sum = random.randint(x, y) # 产生x,y之间一个随机整数
astr = ""
for i in range(str_sum):
astr += random.choice(src)
return astr
def output():
"""
定义输出数据库表中所有记录函数
:return:
"""
# 执行查询
cur.execute("select * from mytab")
# 遍历记录
for sid, name, ps in cur:
print(sid, " ", name, " ", ps) # 输出记录
def out_put_all():
"""
定义输出数据库表中所有记录函数
:return:
"""
cur.execute("select * from mytab")
for item in cur.fetchall():
print(item) # 使用fetchall()函数
def get_data_list(n):
"""
定义生成记录列表数据的函数
:param n:
:return:
"""
res = []
for i in range(n):
res.append((get_str(2, 4), get_str(8, 12)))
return res
if __name__ == '__main__':
print("建立连接.......................")
con = sqlite3.connect("mrsoft.db") # 建立连接使用内存中的数据库
# con = sqlite3.connect("test.db") # 建立连接使用内存中的数据库
print("建立游标.......................")
cur = con.cursor() # 获取游标
print("创建一张表mytab.......................")
cur.execute("create table mytab(id integer primary key autoincrement not null ,name text ,passwd text)")
print("插入一条记录.......................")
cur.execute("insert into mytab(name,passwd)values (?,?)", (get_str(2, 4), get_str(8, 12),)) # 插入1条记录
con.commit()
output() # 显示所有记录
print("批量插入多条记录.......................")
cur.executemany("insert into mytab(name,passwd)values (?,?)", get_data_list(3)) # 插入多条记录
print("显示所有记录........................")
con.commit()
out_put_all() # 显示所有记录
print("更新一条记录..............")
cur.execute("update mytab set name=? where id =?", ("aaa", 1)) # 更新记录
print("显示所有记录.........................")
con.commit()
output() # 显示所有记录
print("删除一条记录.......................")
cur.execute("delete from mytab where id=?", (3,)) # 删除一条记录
con.commit()
print("显示所有记录：")
output() # 显示所有记录
cur.close() # 关闭游标
con.close() # 关闭连接
输出信息
建立连接.......................
建立游标.......................
创建一张表mytab.......................
插入一条记录.......................
1 br mzhourjabh
批量插入多条记录.......................
显示所有记录........................
(1, 'br', 'mzhourjabh')
(2, 'plgz', 'edgujqbe')
(3, 'mz', 'zzkcncpeoc')
(4, 'vxgv', 'xuyxfqkokw')
更新一条记录..............
显示所有记录.........................
1 aaa mzhourjabh
2 plgz edgujqbe
3 mz zzkcncpeoc
4 vxgv xuyxfqkokw
删除一条记录.......................
显示所有记录：
1 aaa mzhourjabh
2 plgz edgujqbe
4 vxgv xuyxfqkokw
* 更新数据库后应该调用connect 对象的commit() 方法来保存更新结果。
1.导入Python SQLite数据模块
#导入模块
import sqlite3
2.建立数据库连接，返回Connection对象
#创建连接对象
conn = sqlite3.connect('mrsoft.db')
不仅可以在硬盘上创建数据库文件，还可以在内存中创建。
conn = sqlite3.connect(':memory:')
3.创建游标对象
#创建游标对象
cursor = conn.cursor()
4.使用cursor对象的execute()方法执行SQL命令，返回结果集
cur.execute(sql) #执行SQL语句
cur.execute(sql,parameters) #执行带参数的SQL语句
cur.executemany(sql,sql_of_parameters) #根据参数执行多次SQL语句
cur.executesript(sql_script) #执行SQL脚本
5.获取游标的查询结果集
cur.fetchone() #返回结果集的下一行（Row对象）;无数据时返回None
cur.fetchall() #返回结果集的剩余行（Row对象列表）;无数据时返回空List
cur.fetchmany() #返回结果集的多行（Row对象列表）;无数据时返回空List
6.数据库的提交和回滚
根据数据库事务隔离级别的不同，可以提交和回滚。
con.commit() #事务提交
con.rollback() #事务回滚
7.关闭Cursor对象和Connection对象
最后需要关闭打开的Cursor对象和Connection对象
cur.close() #关闭Cursor对象
con.close() #关闭Connection对象
13.2.8. Python操作SQLite代码示例¶
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# import MySQLdb #引入Python引擎包
# 连接本机数据库testDB
# conn = MySQLdb.connect(database="testDB", user="user1", password="password123",
# host="127.0.0.1", port=3306)
import os
if os.path.exists('test.db'):
os.remove('test.db')
import sqlite3
conn = sqlite3.connect('test.db')
# 获取游标对象
cur = conn.cursor()
# 执行一系列SQL语句
# 建立一个表
cur.execute("CREATE TABLE demo(num int,str varchar(20));")
# 插入一些记录
cur.execute("INSERT INTO demo VALUES (%d, '%s')" % (1, 'aaa'))
cur.execute("INSERT INTO demo VALUES (%d, '%s')" % (2, 'bbb'))
cur.execute("INSERT INTO demo VALUES (%d, '%s')" % (3, 'ccc'))
# 更新一条记录
cur.execute("UPDATE demo SET str='%s' WHERE num = %d" % ('ddd', 3))
# 查询
cur.execute("SELECT * FROM demo;")
rows = cur.fetchall()
print("number of records: ", len(rows))
for i in rows:
print(i)
# 提交事务
conn.commit()
# 关闭游标对象
cur.close()
# 关闭数据库连接
conn.close()
13.2.9. 操作SQLite的封装类¶
#!/usr/bin/env python
# -*- coding:utf8 -*-
# @auther: 18793
# @Date： 2020/7/17 15:31
# @filename: 操作SQLite.py
# @Email: 1879324764@qq.com
# @Software: PyCharm
import sqlite3
class MySqliteDb(object):
"""Sqlite3 Db Class"""
def __init__(self, dbname="mys.db"):
self.dbname = dbname
self.con = None
self.curs = None
def getCursor(self):
self.con = sqlite3.connect(self.dbname)
if self.con:
self.curs = self.con.cursor()
def closeDb(self):
if self.curs:
self.curs.close()
if self.con:
self.con.commit()
self.con.close()
def __enter__(self):
self.getCursor()
return self.curs
def __exit__(self, exc_type, exc_val, exc_tb):
if exc_val:
print("Exception has generate: ", exc_val)
print("Sqlite3 execute error!")
self.closeDb()
if __name__ == '__main__':
# 建立一个表
with MySqliteDb() as db:
sql = "Create TABLE demo(num int,str varchar(20))"
db.execute(sql)
# 插入一些数据记录
sqls = ("insert into demo values (%d,\"%s\")" % (1, "aaa"),
"insert into demo values (%d,\"%s\")" % (2, "bbb"),
"insert into demo values (%d,\"%s\")" % (3, "ccc"),
)
with MySqliteDb() as db:
for sql in sqls:
db.execute(sql)
# 更新一条记录
with MySqliteDb() as db:
sql = "update demo set str='%s' where num= %d" % ('ddd', 3)
db.execute(sql)
# 查询
with MySqliteDb() as db:
sql = "select * from demo;"
db.execute(sql)
rows = db.fetchall()
print("number of records: ", len(rows))
for row in rows:
print(row)