sqlite数据库在Python中的使用简介
2017-12-08 17:07
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sqlite数据库在Python中的使用简介
1. sqlite3介绍
import sqlite3
SQLite数据库是一款非常小巧的嵌入式开源数据库软件,没有独立的维护进程,所有的维护都来自于程序本身。在python中,使用sqlite3创建数据库的连接,当数据库文件不存在时,会新建数据库文件;如果数据库文件已经存在了,则打开数据库文件。
连接对象可以是硬盘上面的数据库文件,也可以是建立在内存中的,在内存中的数据库执行完任何操作后,不需要提交事务的commit。
#使用:memory:标识打开的是内存数据库 con = sqlite3.connect(":memory:")
#在本地当前目录下创建数据库文件\打开数据库文件-test.db conn = sqlite3.connect('test.db')
打开数据库时返回的对象conn就是一个数据库连接对象,它可以有以下操作:
commit() --事务提交 rollback() --事务回滚 close() --关闭一个数据库链接 cursor() --创建一个游标
创建一个游标对象:cu
cu = conn.cursor()
关闭一个游标对象
cu.close()
在sqlite3中,所有sql语句的执行都要在游标对象的参与下完成
对于游标对象cu,具有以下具体操作:
execute() --执行一条sql语句 executemany() --执行多条sql语句 close() --游标关闭 fetchone() --从结果中取出一条记录 fetchmany() --从结果中取出多条记录 fetchall() --从结果中取出所有记录 scroll() --游标滚动
2. 创建table
创建表(id,name,gender,ag4000
e,address,phone),通过cu.execute(create_table_sql)执行sql语句创建表,如果失败会抛出异常。“table
studentalready exists”,代表已经存在student表,不能再次创建。
create_table_sql = '''CREATE TABLE `student` ( `id` int(11) NOT NULL, `name` varchar(20) NOT NULL, `gender` varchar(4) DEFAULT NULL, `age` int(11) DEFAULT NULL, `address` varchar(200) DEFAULT NULL, `phone` varchar(20) DEFAULT NULL, PRIMARY KEY (`id`) )''' try: conn = sqlite3.connect('test.db') cu = conn.cursor() cu.execute(create_table_sql) print 'table create successful' except sqlite3.Error, why: print 'create table failed:' + why.args[0]
2. 删除table
删除表,删除失败会抛出异常。try: #如果存在表先删除 drop_table_sql = 'DROP TABLE IF EXISTS student' conn = sqlite3.connect('test.db') cu = conn.cursor() cu.execute(drop_table_sql) print 'delete table successful' except sqlite3.Error, why: print 'delete table failed:' + why.args[0]
2. 插入数据
try: save_sql = 'INSERT INTO student values (?, ?, ?, ?, ?, ?)' data = (1, 'zhang', '男', 20, '广东省广州市', '13423****62') conn = sqlite3.connect('test.db') cu = conn.cursor() cu.execute(save_sql, data) print 'save data successful' except sqlite3.Error, why: print 'save data failed:' + why.args[0]
cu.execute(save_sql, data),data参数为元组,如果是其他类型会出现错误提示,上面代码执行完毕之后会提示:
save data failed:You must not use 8-bit bytestrings unless you use a text_factory that can interpret 8-bit bytestrings (like text_factory = str). It is highly recommended that you instead just switch your application to Unicode strings.
是由于中文字符串导致的,请先确定你的IDE或者系统默认编码是utf-8,并且在中文字符串前+u来解决。
data = (1, 'Hongten', u'男', 20, u'广东省广州市', '13423****62')
3. 更新数据
更新数据,把ID等于1的Name更新为James。update_sql = '''UPDATE student SET name = ? WHERE ID = ? ''' data = ('James', 1) try: conn = sqlite3.connect('test.db') cu = conn.cursor() cu.execute(update_sql, data) conn.commit() print 'table update successful' except sqlite3.Error, why: print 'table update failed:' + why.args[0]
4. 查询数据
#查询全部数据 fetchall_sql = '''SELECT * FROM student''' try: conn = sqlite3.connect('test.db') cu = conn.cursor() cu.execute(fetchall_sql) content = cu.fetchall() print content # if len(content) > 0: # for item in content: # for element in item: # print element, # print '' # else: # for element in content: # print element, # print '' except sqlite3.Error as why: print "fetchall data failed:", why.args[0] return
输出:
[(1, u’Zhang’, u’\u7537’, 15, u’\u5e7f\u4e1c\u7701\u5e7f\u5dde\u5e02’, u’13*******62’), (2, u’Li’, u’\u7537’, 22, u’\u7f8e\u56fd\u65e7\u91d1\u5c71’, u’15*******63’), (3, u’Zhao’, u’\u5973’, 18, u’\u5e7f\u4e1c\u7701\u5e7f\u5dde\u5e02’, u’18*******87’), (4, u’Xi’, u’\u5973’, 21, u’\u5e7f\u4e1c\u7701\u5e7f\u5dde\u5e02’, u’14323****32’)]
中文部分仍然显示为乱码,如果要显示出中文字体,那需要按注释部分,依次打印出每个字符串
#查询一条数据 fetchall_sql = '''SELECT * FROM student WHERE ID = ? ''' data = 1 try: conn = sqlite3.connect('test.db') cu = conn.cursor() d = (data,) cu.execute(fetchall_sql, d) content = cu.fetchall() if len(content) > 0: for item in content: for element in item: print element, print '' else: for element in content: print element, print '' print 'fetch the data successful' except sqlite3.Error, why: print 'fetch data failed:' + why.args[0]
5. 删除数据
把WHERE后面的去掉,’DELETE FROM student’,删除全部数据#删除一条数据 '''DELETE FROM student WHERE ID = ? AND NAME = ?''' data = (1, 'James') try: conn = sqlite3.connect('test.db') cu = conn.cursor() cu.execute(update_sql, data) conn.commit() print 'delete data successful' except sqlite3.Error, why: print 'delete data failed:' + why.args[0]
以下是封装成类后的全部代码,新人代码,如果出现问题请多多交流
# coding:utf-8 """ @author: smartgang @contact: zhangxingang92@qq.com @file: SqliteHelper.py @time: 2017/12/7 18:19 """ import sqlite3 ''' SQLite数据库是一款非常小巧的嵌入式开源数据库软件,没有独立的维护进程,所有的维护都来自于程序本身。在python中,使用sqlite3创建数据库的连接,当数据库文件不存在时,会新建数据库文件;如果数据库文件已经存在了,则打开数据库文件。 连接对象可以是硬盘上面的数据库文件,也可以是建立在内存中的,在内存中的数据库执行完任何操作后,不需要提交事务的commit。 使用:memory:标识打开的是内存数据库 con = sqlite3.connect(":memory:") 在本地当前目录下创建数据库文件\打开数据库文件-test.db conn = sqlite3.connect('test.db') 打开数据库时返回的对象conn就是一个数据库连接对象,它可以有以下操作: commit() --事务提交 rollback() --事务回滚 close() --关闭一个数据库链接 cursor() --创建一个游标 创建一个游标对象:cu cu = conn.cursor() 关闭一个游标对象 cu.close() 在sqlite3中,所有sql语句的执行都要在游标对象的参与下完成 对于游标对象cu,具有以下具体操作: execute() --执行一条sql语句 executemany() --执行多条sql语句 close() --游标关闭 fetchone() --从结果中取出一条记录 fetchmany() --从结果中取出多条记录 fetchall() --从结果中取出所有记录 scroll() --游标滚动 ''' class SqliteHelper: def __init__(self, dataFile): try: self.conn = sqlite3.connect(dataFile) except sqlite3.Error as e: print "连接sqlite数据库失败:", e.args[0] def getcursor(self): return self.conn.cursor() def drop(self, table): ''' if the table exist,please be carefull ''' if table is not None and table != '': cu = self.getcursor() sql = 'DROP TABLE IF EXISTS ' + table try: cu.execute(sql) except sqlite3.Error as why: print "delete table failed:", why.args[0] return self.conn.commit() print "delete table successful!" cu.close() else: print "table does not exist!" def create(self, sql): ''' create database table :param sql: :return: ''' if sql is not None and sql != '': cu = self.getcursor() try: cu.execute(sql) except sqlite3.Error as why: print "create table failed:", why.args[0] return self.conn.commit() print "create table successful!" cu.close() else: print "sql is empty or None" def insert(self, d2ff sql, data): ''' insert data to the table :param sql: :param data: :return: ''' if sql is not None and sql != '': if data is not None: cu = self.getcursor() try: for d in data: cu.execute(sql, d) self.conn.commit() except sqlite3.Error as why: print "insert data failed:", why.args[0] cu.close() else: print "sql is empty or None" def fetchall(self, sql): ''' query all data :param sql: :return: ''' if sql is not None and sql != '': cu = self.getcursor() try: cu.execute(sql) content = cu.fetchall() if len(content) > 0: for item in content: for element in item: print element, print '' else: for element in content: print element, print '' except sqlite3.Error as why: print "fetchall data failed:", why.args[0] cu.close() else: print "sql is empty or None" def fetchone(self, sql, data): ''' query one data :param sql: :param data: :return: ''' if sql is not None and sql != '': if data is not None: cu = self.getcursor() try: d = (data,) cu.execute(sql, d) content = cu.fetchall() if len(content) > 0: for item in content: for element in item: print element, print '' else: for element in content: print element, print '' except sqlite3.Error as why: print "fetch the data failed:", why.args[0] return cu.close() else: print "sql is empty or None" def update(self, sql, data): ''' update the data :param sql: :param data: :return: ''' if sql is not None and sql != '': if data is not None: cu = self.getcursor() try: for d in data: cu.execute(sql, d) self.conn.commit() except sqlite3.Error as why: print "update data failed:", why.args[0] cu.close() else: print "sql is empty or None" def delete(self, sql, data=None): ''' delete the data :param sql: :param data: :return: ''' if sql is not None and sql != '': cu = self.getcursor() if data is not None: try: for d in data: cu.execute(sql, d) self.conn.commit() except sqlite3.Error as why: print "delete data failed:", why.args[0] else: try: cu.execute(sql) self.conn.commit() except sqlite3.Error as why: print "delete data failed:", why.args[0] cu.close() else: print "sql is empty or None" def __del__(self): self.conn.close() # test TABLE_NAME = 'student' def drop_table_test(): '''删除数据库表测试''' print('删除数据库表测试...') sqlhelper = SqliteHelper('test.db') sqlhelper.drop(TABLE_NAME) def create_table_test(): '''创建数据库表测试''' print('创建数据库表测试...') # 创建表(id,name,gender,age,address,phone) create_table_sql = '''CREATE TABLE `student` ( `id` int(11) NOT NULL, `name` varchar(20) NOT NULL, `gender` varchar(4) DEFAULT NULL, `age` int(11) DEFAULT NULL, `address` varchar(200) DEFAULT NULL, `phone` varchar(20) DEFAULT NULL, PRIMARY KEY (`id`) )''' sqlhelper = SqliteHelper('test.db') sqlhelper.create(create_table_sql) sqlhelper = SqliteHelper('test.db') def save_test(): '''保存数据测试...''' print('保存数据测试...') save_sql = 'INSERT INTO student values (?, ?, ?, ?, ?, ?)' data = [(1, 'Zhang', u'男', 15, u'北京', '12345678910'), (2, 'Li', u'男', 50, u'吉林省长春市', '1567891****'), (3, 'Zhao', u'女', 40, u'黑龙江', '18*********'), (4, 'Xi', u'女', 30, u'上海', '1**********'), (5, 'Liao', u'男', 15, u'湖南', '12345678910'), (6, 'Ling', u'男', 50, u'大理', '1567891****'), (7, 'JJJ', u'女', 40, u'***', '18*********'), (8, 'LLL', u'女', 30, u'Hongkong', '1**********')] sqlhelper.insert(save_sql, data) def fetchall_test(): '''查询所有数据...''' print('查询所有数据...') fetchall_sql = '''SELECT * FROM student''' sqlhelper.fetchall(fetchall_sql) def fetchone_test(): '''查询所有数据...''' print('查询一条数据...') fetchall_sql = '''SELECT * FROM student WHERE ID = ? ''' data = 1 sqlhelper.fetchone(fetchall_sql, data) update_sql = '''UPDATE student SET name = ? WHERE ID = ? ''' data = [(1, 'James'), (2, 'Kobe')] sqlhelper.update(update_sql, data) def update_test(): '''更新数据''' print('更新一条数据...') update_sql = '''UPDATE student SET name = ? WHERE ID = ? ''' data = [('James', 1), ('Kobe', 2)] sqlhelper.update(update_sql, data) def delete_test(): '''删除数据''' print('删除一条数据...') update_sql = '''DELETE FROM student WHERE ID = ? AND NAME = ?''' data = [(1, 'James')] sqlhelper.delete(update_sql, data) drop_table_test() create_table_test() save_test() update_test() delete_test()
参考文章:
用Python进行SQLite数据库操作
python开发sqlite3绝对完整_博主推荐
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