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python 判断 null

草原上的骆驼 — Sun, 14 Aug 2011 00:47:00 GMT

if not result2 is None :

if result is None

注意是大�?img src ="http://www.aygfsteel.com/nkjava/aggbug/356482.html" width = "1" height = "1" />

草原上的骆驼 2011-08-14 08:47 发表评论

Python �q�接 Mysql

草原上的骆驼 — Sun, 14 Aug 2011 00:46:00 GMT

�q�接Mysql

#coding=utf-8

#MySQLdb �C�Z��
#
##################################
import MySQLdb

#建立和数据库�pȝ��的连�?br />conn = MySQLdb.connect(host='localhost', user='root',passwd='longforfreedom')

#获取操作游标
cursor = conn.cursor()
#执行SQL,创徏一个数据库.
cursor.execute("""create database python """)

#关闭�q�接�Q�释放资�?br />cursor.close();

插入数据、批量插入数�?br />

#coding=utf-8
###################################
# @author migle
# @date 2010-01-17
##################################
#MySQLdb �C�Z��
#
##################################
import MySQLdb

#建立和数据库�pȝ��的连�?br />conn = MySQLdb.connect(host='localhost', user='root',passwd='21ccvn')

#获取操作游标
cursor = conn.cursor()
#执行SQL,创徏一个数据库.
cursor.execute("""create database if not exists 21ccvn""")

#选择数据�?br />conn.select_db('21ccvn');
#执行SQL,创徏一个数据表.
cursor.execute("""create table 21ccvn(id int, info varchar(100)) """)

value = [1,"inserted ?"];

#插入一条记�?br />cursor.execute("insert into test values(%s,%s)",value);

values=[]

#生成插入参数�?br />for i in range(20):
values.append((i,'Hello mysqldb, I am recoder ' + str(i)))
#插入多条记录

cursor.executemany("""insert into test values(%s,%s) """,values);

#关闭�q�接�Q�释放资�?br />cursor.close();

查询�Q�获取一个，获取多个�Q�获取所有记录数

#coding=utf-8

#
# MySQLdb 查询
#
#######################################

import MySQLdb

conn = MySQLdb.connect(host='localhost', user='root', passwd='longforfreedom',db='21ccvn')

cursor = conn.cursor()

count = cursor.execute('select * from test')

print '��d��?nbsp;%s 条记�?/span>',count

#获取一条记�?每条记录做�ؓ一个元�l�返�?br />print "只获取一条记�?"
result = cursor.fetchone();
print result
#print 'ID: %s   info: %s' % (result[0],result[1])
print 'ID: %s   info: %s' % result

#获取5条记录，注意�׃��之前执行有了fetchone()�Q�所以游标已�l�指到第二条记录了，也就是从�W�二条开始的所有记�?br />print "只获�?条记�?"
results = cursor.fetchmany(5)
for r in results:
    print r

print "获取所有结�?"
#重置游标位置�Q?/span>0,为偏�U�量�Q�mode�Q�absolute | relative,默认为relative,
cursor.scroll(0,mode='absolute')
#获取所有结�?br />results = cursor.fetchall()
for r in results:
    print r
conn.close()

草原上的骆驼 2011-08-14 08:46 发表评论

python的time和date处理

草原上的骆驼 — Fri, 04 Mar 2011 08:23:00 GMT

内置模块time包含很多与时间相兛_��数。我们可通过它获得当前的旉��和格式化旉��输出�?/p>

time()�Q�以��点形式�q�回自Linux��C��U�以来经�q�的�U�数。在linux中，00:00:00 UTC, January 1, 1970是新**49**的开始�?/p>
strftime可以用来获得当前旉��Q�可以将旉��格式化�ؓ字符串等�{�，�q�挺方便的。但是需要注意的是获得的旉��是服务器的时��_��注意时区问题�Q�比如gae撒谎那个的时间就是格林尼��L��间的0时区�Q�需要自��p�{换�?br />
strftime�Q�）函数��时间格式化
我们可以使用strftime�Q�）函数��时间格式化为我们想要的格式。它的原型如下：

size_t strftime(
char *strDest,
size_t maxsize,
const char *format,
const struct tm *timeptr
);

我们可以�Ҏ��format指向字符串中格式命��o把timeptr中保存的旉��信息攑֜�strDest指向的字�W�串中，最多向strDest中存放maxsize个字�W�。该函数�q�回向strDest指向的字�W�串中放�|�的字符数�?br />
strftime使时间格式化。python的strftime格式是C库支持的旉��格式的真子集�?br />
　　%a 星期几的��?Weekday name, abbr.
　　%A 星期几的全称 Weekday name, full
　　%b 月分的简�?Month name, abbr.
　　%B 月䆾的全�U?Month name, full
　　%c 标准的日期的旉��?Complete date and time representation
　　%d 十进制表�C�的每月的第几天 Day of the month
　　%H 24��时制的��时 Hour (24-hour clock)
　　%I 12��时制的��时 Hour (12-hour clock)
　　%j 十进制表�C�的每年的第几天 Day of the year
　　%m 十进制表�C�的月䆾 Month number
　　%M 十时制表�C�的分钟�?Minute number
　　%S 十进制的�U�数 Second number
　　%U �W�年的第几周�Q�把星期日做为第一天（��g��0�?3�Q�Week number (Sunday first weekday)
　　%w 十进制表�C�的星期几（��g��0�?�Q�星期天�?�Q�weekday number
　　%W 每年的第几周�Q�把星期一做�ؓ�W�一天（��g��0�?3�Q?Week number (Monday first weekday)
　　%x 标准的日期串 Complete date representation (e.g. 13/01/08)
　　%X 标准的时间串 Complete time representation (e.g. 17:02:10)
　　%y 不带世纪的十�q�制�q�䆾�Q��g��0�?9�Q�Year number within century
　　%Y 带世�U�部分的十制�q�䆾 Year number
　　%z�Q?Z 时区名称�Q�如果不能得到时区名�U�则�q�回�I�字�W�。Name of time zone
　　%% 癑ֈ��?

1. # handling date/time data 2. # Python23 tested vegaseat 3/6/2005 3. 4. import time 5. 6. print "List the functions within module time:" 7. for funk in dir(time): 8. print funk 9. 10. print time.time(), "seconds since 1/1/1970 00:00:00" 11. print time.time()/(60*60*24), "days since 1/1/1970" 12. 13. # time.clock() gives wallclock seconds, accuracy better than 1 ms 14. # time.clock() is for windows, time.time() is more portable 15. print "Using time.clock() = ", time.clock(), "seconds since first call to clock()" 16. print "\nTiming a 1 million loop 'for loop' ..." 17. start = time.clock() 18. for x in range(1000000): 19. y = x # do something 20. end = time.clock() 21. print "Time elapsed = ", end - start, "seconds" 22. 23. # create a tuple of local time data 24. timeHere = time.localtime() 25. print "\nA tuple of local date/time data using time.localtime():" 26. print "(year,month,day,hour,min,sec,weekday(Monday=0),yearday,dls-flag)" 27. print timeHere 28. 29. # extract a more readable date/time from the tuple 30. # eg. Sat Mar 05 22:51:55 2005 31. print "\nUsing time.asctime(time.localtime()):", time.asctime(time.localtime()) 32. # the same results 33. print "\nUsing time.ctime(time.time()):", time.ctime(time.time()) 34. print "\nOr using time.ctime():", time.ctime() 35. 36. print "\nUsing strftime():" 37. print "Day and Date:", time.strftime("%a %m/%d/%y", time.localtime()) 38. print "Day, Date :", time.strftime("%A, %B %d, %Y", time.localtime()) 39. print "Time (12hr) :", time.strftime("%I:%M:%S %p", time.localtime()) 40. print "Time (24hr) :", time.strftime("%H:%M:%S", time.localtime()) 41. print "DayMonthYear:",time.strftime("%d%b%Y", time.localtime()) 42. 43. print 44. 45. print "Start a line with this date-time stamp and it will sort:",\ 46. time.strftime("%Y/%m/%d %H:%M:%S", time.localtime()) 47. 48. print 49. 50. def getDayOfWeek(dateString): 51. # day of week (Monday = 0) of a given month/day/year 52. t1 = time.strptime(dateString,"%m/%d/%Y") 53. # year in time_struct t1 can not go below 1970 (start of epoch)! 54. t2 = time.mktime(t1) 55. return(time.localtime(t2)[6]) 56. 57. Weekday = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 58. 'Friday', 'Saturday', 'Sunday'] 59. 60. # sorry about the limitations, stay above 01/01/1970 61. # more exactly 01/01/1970 at 0 UT (midnight Greenwich, England) 62. print "11/12/1970 was a", Weekday[getDayOfWeek("11/12/1970")] 63. 64. print 65. 66. print "Calculate difference between two times (12 hour format) of a day:" 67. time1 = raw_input("Enter first time (format 11:25:00AM or 03:15:30PM): ") 68. # pick some plausible date 69. timeString1 = "03/06/05 " + time1 70. # create a time tuple from this time string format eg. 03/06/05 11:22:00AM 71. timeTuple1 = time.strptime(timeString1, "%m/%d/%y %I:%M:%S%p") 72. 73. #print timeTuple1 # test eg. (2005, 3, 6, 11, 22, 0, 5, 91, -1) 74. 75. time2 = raw_input("Enter second time (format 11:25:00AM or 03:15:30PM): ") 76. # use same date to stay in same day 77. timeString2 = "03/06/05 " + time2 78. timeTuple2 = time.strptime(timeString2, "%m/%d/%y %I:%M:%S%p") 79. 80. # mktime() gives seconds since epoch 1/1/1970 00:00:00 81. time_difference = time.mktime(timeTuple2) - time.mktime(timeTuple1) 82. #print type(time_difference) # test <type 'float'> 83. print "Time difference = %d seconds" % int(time_difference) 84. print "Time difference = %0.1f minutes" % (time_difference/60.0) 85. print "Time difference = %0.2f hours" % (time_difference/(60.0*60)) 86. 87. print 88. 89. print "Wait one and a half seconds!" 90. time.sleep(1.5) 91. print "The end!"

草原上的骆驼 2011-03-04 16:23 发表评论

Python IO

草原上的骆驼 — Fri, 04 Mar 2011 08:10:00 GMT

1.open

使用open打开文�g后一定要记得调用文�g对象的close()�Ҏ��。比如可以用try/finally语句来确保最后能关闭文�g�?/p>

file_object = open('thefile.txt')
try:
all_the_text = file_object.read( )
finally:
file_object.close( )

注：不能把open语句攑֜�try块里�Q�因为当打开文�g出现异常�Ӟ��文�g对象file_object无法执行close()�Ҏ��?/p>

2.��L��?/span>

��L��本文�?/h4>
input = open('data', 'r')
#�W�二个参数默认�ؓr
input = open('data')

��M��q�制文�g

input = open('data', 'rb')

��d��所有内�?/h4>
file_object = open('thefile.txt')
try:
all_the_text = file_object.read( )
finally:
file_object.close( )

��d��定字�?/h4>
file_object = open('abinfile', 'rb')
try:
    while True:
         chunk = file_object.read(100)
        if not chunk:
            break
         do_something_with(chunk)
finally:
     file_object.close( )

��L��?/h4>
list_of_all_the_lines = file_object.readlines( )

如果文�g是文本文�Ӟ��q�可以直接遍历文件对象获取每行：

for line in file_object:
process line

3.写文�?/span>

写文本文�?/h4>
output = open('data', 'w')

写二�q�制文�g

output = open('data', 'wb')

�q�加写文�?/h4>
output = open('data', 'w+')

写数�?/h4>
file_object = open('thefile.txt', 'w')
file_object.write(all_the_text)
file_object.close( )

写入多行

file_object.writelines(list_of_text_strings)

注意�Q�调用writelines写入多行在性能上会比��用write一�ơ性写入要高�?/p>

在处理日志文件的时候，常常会遇到这��L��情况�Q�日志文件巨大，不可能一�ơ性把整个文�g��d��到内存中�q�行处理�Q�例如需要在一台物理内存�ؓ 2GB 的机器上处理一�?2GB 的日志文�Ӟ��我们可能希望每次只处理其�?200MB 的内宏V�?br style="line-height: normal" /> �?Python 中，内置�?File 对象直接提供了一�?readlines(sizehint) 函数来完成这��L��事情。以下面的代码�ؓ例：

file = open('test.log', 'r')

sizehint = 209715200   # 200M

position = 0

lines = file.readlines(sizehint)

while not file.tell() - position < 0:

       position = file.tell()

       lines = file.readlines(sizehint)

每次调用 readlines(sizehint) 函数�Q�会�q�回大约 200MB 的数据，而且所�q�回的必焉��是完整的行数据，大多数情况下�Q�返回的数据的字节数会稍微比 sizehint 指定的值大一点（除最后一�ơ调�?readlines(sizehint) 函数的时候）。通常情况下，Python 会自动将用户指定�?sizehint 的��D��整成内部�~�存大小的整数倍�?/div>

file在python是一个特�D�的�c�d��Q�它用于在python�E�序中对外部的文件进行操作。在python中一切都是对象，file也不例外�Q�file有file的方法和属性。下面先来看如何创徏一个file对象�Q?/div>

file(name[, mode[, buffering]])

file()函数用于创徏一个file对象�Q�它有一个别名叫open()�Q�可能更形象一些，它们是内�|�函数。来看看它的参数。它参数都是以字�W�串的�Ş式传递的。name是文件的名字�?/div>

mode是打开的模式，可选的��gؓr w a U�Q�分别代表读�Q�默认） �?��d�� 支持各种换行�W�的模式。用w或a模式打开文�g的话�Q�如果文件不存在�Q�那么就自动创徏。此外，用w模式打开一个已�l�存在的文�g�Ӟ��原有文�g的内容会被清�I�，因�ؓ一开始文件的操作的标记是在文件的开头的�Q�这时候进行写操作�Q�无疑会把原有的内容�l�抹掉。由于历史的原因�Q�换行符在不同的�pȝ��中有不同模式�Q�比如在 unix中是一个\n�Q�而在windows中是‘\r\n’�Q�用U模式打开文�g�Q�就是支持所有的换行模式�Q�也��p��‘\r’ '\n' '\r\n'都可表示换行�Q�会有一个tuple用来存贮�q�个文�g中用到过的换行符。不�q�，虽说换行有多�U�模式，��d��python中统一用\n代替。在模式字符的后面，�q�可以加�? b t�q�两�U�标识，分别表示可以�Ҏ��件同时进行读写操作和用二�q�制模式、文本模式（默认�Q�打开文�g�?/div>

buffering如果�?表示不进行缓�?如果�?表示�q�行“行缓�?#8220;;如果是一个大�?的数表示�~�冲区的大小�Q�应该是以字节�ؓ单位的�?/div>

file对象有自��q��属性和�Ҏ��。先来看看file的属性�?/div>

closed #标记文�g是否已经关闭�Q�由close()改写

encoding #文�g�~�码

mode #打开模式

name #文�g�?/div>

newlines #文�g中用到的换行模式�Q�是一个tuple

softspace #boolean型，一般�ؓ0�Q�据说用于print

file的读写方法：

F.read([size]) #size��取的长度�Q�以byte为单�?/div>

F.readline([size])

#��M��行，如果定义了size�Q�有可能�q�回的只是一行的一部分

F.readlines([size])

#把文件每一行作��Z��个list的一个成员，�q�返回这个list。其实它的内部是通过循环调用readline()来实现的。如果提供size参数�Q�size是表�C��取内容的总长�Q�也��是说可能只��d��文�g的一部分�?/div>

F.write(str)

#把str写到文�g中，write()�q�不会在str后加上一个换行符

F.writelines(seq)

#把seq的内容全部写到文件中。这个函��C��只是忠实地写入，不会在每行后面加上�Q何东�ѝ�?/div>

file的其他方法：

F.close()

#关闭文�g。python会在一个文件不用后自动关闭文�g�Q�不�q�这一功能没有保证�Q�最好还是养成自己关闭的习惯。如果一个文件在关闭后还对其�q�行操作会��生ValueError

F.flush()

#把缓冲区的内容写入硬�?/div>

F.fileno()

#�q�回一个长整型�?#8221;文�g标签“

F.isatty()

#文�g是否是一个终端设备文�Ӟ��unix�pȝ��中的�Q?/div>

F.tell()

#�q�回文�g操作标记的当前位�|�，以文件的开头�ؓ原点

F.next()

#�q�回下一行，�q�将文�g操作标记位移��C��一行。把一个file用于for ... in file�q�样的语句时�Q�就是调用next()函数来实现遍历的�?/div>

F.seek(offset[,whence])

#��文件打操作标记�U�d��offset的位�|�。这个offset一般是相对于文件的开头来计算的，一般�ؓ正数。但如果提供了whence参数��׃��一定了�Q�whence可以�?表示从头开始计��，1表示以当前位�|��ؓ原点计算�?表示以文件末��ؓ原点�q�行计算。需要注意，如果文�g以a或a+的模式打开�Q�每�ơ进行写操作�Ӟ��文�g操作标记会自动返回到文�g末尾�?/div>

F.truncate([size])

#把文件裁成规定的大小�Q�默认的是裁到当前文件操作标记的位置。如果size比文件的大小�q�要大，依据�pȝ��的不同可能是不改变文�Ӟ��也可能是�?把文件补到相应的大小�Q�也可能是以一些随机的内容加上厅R�?/div>

草原上的骆驼 2011-03-04 16:10 发表评论

Python Mysql

草原上的骆驼 — Fri, 04 Mar 2011 08:09:00 GMT

http://www.kitebird.com/articles/pydbapi.html

http://www.codegood.com/ python mysql驱动下蝲大全

the Python standard for database interfaces is the Python DB-API. Most Python database interfaces adhere to this standard.

You can choose the right database for your application. Python Database API supports a wide range of database servers:

GadFly
mSQL
MySQL
PostgreSQL
Microsoft SQL Server 2000
Informix
Interbase
Oracle
Sybase

Here is the list of available Python databases interfaces:

Python Database Interfaces and APIs

You must download a separate DB API module for each database you need to access. For example, if you need to access an Oracle database as well as a MySQL database, you must download both the Oracle and the MySQL database modules.

The DB API provides a minimal standard for working with databases, using Python structures and syntax wherever possible. This API includes the following:

Importing the api module.
Acquiring a connection with the database.
Issuing SQL statements and stored procedures.
Closing the connection

We would learn all the concepts using MySQL so let's talk about MySQLdb module only.

What is MySQLdb?

MySQLdb is an interface for connecting to a MySQL database server from Python. It implements the Python Database API v2.0, and is built on top of the MySQL C API.

How do I install the MySQLdb?

Before proceeding you make sure you have MySQLdb installed on your machine. Just type the following in your Python script and execute it:

#!/usr/bin/python
            import MySQLdb

If it produces following result then it means MySQLdb module is not installed:

Traceback (most recent call last):
            File "test.py", line 3, in 
            import MySQLdb
            ImportError: No module named MySQLdb

To install MySQLdb module, download it from MySQLdb Download page and proceed as follows:

$ gunzip MySQL-python-1.2.2.tar.gz
            $ tar -xvf MySQL-python-1.2.2.tar
            $ cd MySQL-python-1.2.2
            $ python setup.py build
            $ python setup.py install

Note: Make sure you have root privilege to install above module.

Database Connection:

Before connecting to a MySQL database make sure followings:

You have created a database TESTDB.
You have created a table EMPLOYEE in TESTDB.
This table is having fields FIRST_NAME, LAST_NAME, AGE, SEX and INCOME.
User ID "testuser" and password "test123" are set to access TESTDB
Python module MySQLdb is installed properly on your machine.
You have gone through MySQL tutorial to understand MySQL Basics.

Example:

Following is the example of connecting with MySQL database "TESTDB"

#!/usr/bin/python
            import MySQLdb
            # Open database connection
            db = MySQLdb.connect("localhost","testuser","test123","TESTDB" )
            # prepare a cursor object using cursor() method
            cursor = db.cursor()
            # execute SQL query using execute() method.
            cursor.execute("SELECT VERSION()")
            # Fetch a single row using fetchone() method.
            data = cursor.fetchone()
            print "Database version : %s " % data
            # disconnect from server
            db.close()

While running this script, its producing following result at my Linux machine.

Database version : 5.0.45

If a connection is established with the datasource then a Connection Object is returned and saved into db for further use otherwise db is set to None. Next db object is used to create a cursor object which in turn is used to execute SQL queries.

Finally before coming out it ensures that database connection is closed and resources are released.

Creating Database Table:

Once a database connection is established, we are ready to create tables or records into the database tables using execute method of the created cursor.

Example:

First let's create Database table EMPLOYEE:

#!/usr/bin/python
            import MySQLdb
            # Open database connection
            db = MySQLdb.connect("localhost","testuser","test123","TESTDB" )
            # prepare a cursor object using cursor() method
            cursor = db.cursor()
            # Drop table if it already exist using execute() method.
            cursor.execute("DROP TABLE IF EXISTS EMPLOYEE")
            # Create table as per requirement
            sql = """CREATE TABLE EMPLOYEE (
            FIRST_NAME  CHAR(20) NOT NULL,
            LAST_NAME  CHAR(20),
            AGE INT,
            SEX CHAR(1),
            INCOME FLOAT )"""
            cursor.execute(sql)
            # disconnect from server
            db.close()

INSERT Operation:

INSERT operation is required when you want to create your records into a database table.

Example:

Following is the example which executes SQL INSERT statement to create a record into EMPLOYEE table.

#!/usr/bin/python
            import MySQLdb
            # Open database connection
            db = MySQLdb.connect("localhost","testuser","test123","TESTDB" )
            # prepare a cursor object using cursor() method
            cursor = db.cursor()
            # Prepare SQL query to INSERT a record into the database.
            sql = """INSERT INTO EMPLOYEE(FIRST_NAME,
            LAST_NAME, AGE, SEX, INCOME)
            VALUES ('Mac', 'Mohan', 20, 'M', 2000)"""
            try:
            # Execute the SQL command
            cursor.execute(sql)
            # Commit your changes in the database
            db.commit()
            except:
            # Rollback in case there is any error
            db.rollback()
            # disconnect from server
            db.close()

Above example can be written as follows to create SQL queries dynamically:

#!/usr/bin/python
            import MySQLdb
            # Open database connection
            db = MySQLdb.connect("localhost","testuser","test123","TESTDB" )
            # prepare a cursor object using cursor() method
            cursor = db.cursor()
            # Prepare SQL query to INSERT a record into the database.
            sql = "INSERT INTO EMPLOYEE(FIRST_NAME, \
            LAST_NAME, AGE, SEX, INCOME) \
            VALUES ('%s', '%s', '%d', '%c', '%d' )" % \
            ('Mac', 'Mohan', 20, 'M', 2000)
            try:
            # Execute the SQL command
            cursor.execute(sql)
            # Commit your changes in the database
            db.commit()
            except:
            # Rollback in case there is any error
            db.rollback()
            # disconnect from server
            db.close()

Example:

Following code segment is another form of execute where you can pass parameters directly:

..................................
            user_id = "test123"
            password = "password"
            con.execute('insert into Login values("%s", "%s")' % \
            (user_id, password))
            ..................................

READ Operation:

READ Operation on any databasse means to fetch some useful information from the database.

Once our database connection is established, we are ready to make a query into this database. We can use either fetchone() method to fetch single record or fetchall method to fetech multiple values from a database table.

fetchone(): This method fetches the next row of a query result set. A result set is an object that is returned when a cursor object is used to query a table.
fetchall(): This method fetches all the rows in a result set. If some rows have already been extracted from the result set, the fetchall() method retrieves the remaining rows from the result set.
rowcount: This is a read-only attribute and returns the number of rows that were affected by an execute() method.

Example:

Following is the procedure to query all the records from EMPLOYEE table having salary more than 1000.

#!/usr/bin/python
            import MySQLdb
            # Open database connection
            db = MySQLdb.connect("localhost","testuser","test123","TESTDB" )
            # prepare a cursor object using cursor() method
            cursor = db.cursor()
            # Prepare SQL query to INSERT a record into the database.
            sql = "SELECT * FROM EMPLOYEE \
            WHERE INCOME > '%d'" % (1000)
            try:
            # Execute the SQL command
            cursor.execute(sql)
            # Fetch all the rows in a list of lists.
            results = cursor.fetchall()
            for row in results:
            fname = row[0]
            lname = row[1]
            age = row[2]
            sex = row[3]
            income = row[4]
            # Now print fetched result
            print "fname=%s,lname=%s,age=%d,sex=%s,income=%d" % \
            (fname, lname, age, sex, income )
            except:
            print "Error: unable to fecth data"
            # disconnect from server
            db.close()

This will produce following result:

fname=Mac, lname=Mohan, age=20, sex=M, income=2000

Update Operation:

UPDATE Operation on any databasse means to update one or more records which are already available in the database. Following is the procedure to update all the records having SEX as 'M'. Here we will increase AGE of all the males by one year.

Example:

#!/usr/bin/python
            import MySQLdb
            # Open database connection
            db = MySQLdb.connect("localhost","testuser","test123","TESTDB" )
            # prepare a cursor object using cursor() method
            cursor = db.cursor()
            # Prepare SQL query to UPDATE required records
            sql = "UPDATE EMPLOYEE SET AGE = AGE + 1
            WHERE SEX = '%c'" % ('M')
            try:
            # Execute the SQL command
            cursor.execute(sql)
            # Commit your changes in the database
            db.commit()
            except:
            # Rollback in case there is any error
            db.rollback()
            # disconnect from server
            db.close()

DELETE Operation:

DELETE operation is required when you want to delete some records from your database. Following is the procedure to delete all the records from EMPLOYEE where AGE is more than 20.

Example:

#!/usr/bin/python
            import MySQLdb
            # Open database connection
            db = MySQLdb.connect("localhost","testuser","test123","TESTDB" )
            # prepare a cursor object using cursor() method
            cursor = db.cursor()
            # Prepare SQL query to DELETE required records
            sql = "DELETE FROM EMPLOYEE WHERE AGE > '%d'" % (20)
            try:
            # Execute the SQL command
            cursor.execute(sql)
            # Commit your changes in the database
            db.commit()
            except:
            # Rollback in case there is any error
            db.rollback()
            # disconnect from server
            db.close()

Performing Transactions:

Transactions are a mechanism that ensures data consistency. Transactions should have the following four properties:

Atomicity: Either a transaction completes or nothing happens at all.
Consistency: A transaction must start in a consistent state and leave the system is a consistent state.
Isolation: Intermediate results of a transaction are not visible outside the current transaction.
Durability: Once a transaction was committed, the effects are persistent, even after a system failure.

The Python DB API 2.0 provides two methods to either commit or rollback a transaction.

Example:

You already have seen how we have implemented transations. Here is again similar example:

# Prepare SQL query to DELETE required records
            sql = "DELETE FROM EMPLOYEE WHERE AGE > '%d'" % (20)
            try:
            # Execute the SQL command
            cursor.execute(sql)
            # Commit your changes in the database
            db.commit()
            except:
            # Rollback in case there is any error
            db.rollback()

COMMIT Operation:

Commit is the operation which gives a green signal to database to finalize the changes and after this operation no change can be reverted back.

Here is a simple example to call commit method.

    db.commit()

ROLLBACK Operation:

If you are not satisfied with one or more of the changes and you want to revert back those changes completely then use rollback method.

Here is a simple example to call rollback metho.

   db.rollback()

Disconnecting Database:

To disconnect Database connection, use close() method.

    db.close()

If the connection to a database is closed by the user with the close() method, any outstanding transactions are rolled back by the DB. However, instead of depending on any of DB lower level implementation details, your application would be better off calling commit or rollback explicitly.

Handling Errors:

There are many sources of errors. A few examples are a syntax error in an executed SQL statement, a connection failure, or calling the fetch method for an already canceled or finished statement handle.

The DB API defines a number of errors that must exist in each database module. The following table lists these exceptions.

Exception	Description
Warning	Used for non-fatal issues. Must subclass StandardError.
Error	Base class for errors. Must subclass StandardError.
InterfaceError	Used for errors in the database module, not the database itself. Must subclass Error.
DatabaseError	Used for errors in the database. Must subclass Error.
DataError	Subclass of DatabaseError that refers to errors in the data.
OperationalError	Subclass of DatabaseError that refers to errors such as the loss of a connection to the database. These errors are generally outside of the control of the Python scripter.
IntegrityError	Subclass of DatabaseError for situations that would damage the relational integrity, such as uniqueness constraints or foreign keys.
InternalError	Subclass of DatabaseError that refers to errors internal to the database module, such as a cursor no longer being active.
ProgrammingError	Subclass of DatabaseError that refers to errors such as a bad table name and other things that can safely be blamed on you.
NotSupportedError	Subclass of DatabaseError that refers to trying to call unsupported functionality.

Your Python scripts should handle these errors but before using any of the above exceptions, make sure your MySQLdb has support for that exception. You can get more information about them by reading the DB API 2.0 specification.

草原上的骆驼 2011-03-04 16:09 发表评论

python 中文��q��

草原上的骆驼 — Fri, 04 Mar 2011 08:07:00 GMT

http://bbs.quickbest.com.cn/thread-38962-1-1.html

草原上的骆驼 2011-03-04 16:07 发表评论

草原上的骆驼 — Fri, 04 Mar 2011 08:06:00 GMT

摘要: http://www.cnblogs.com/huxi/archive/2010/07/04/1771073.html 1. 正则表达式基�� 1.1. ��单介�l?正则表达式�ƈ不是Python的一部分。正则表辑ּ�是用于处理字�W�串的强大工��P��拥有自己独特的语法以及一个独立的处理引擎�Q�效率上可能不如str自带的方法，但功能十分强大。得益于�q�一点，在提供了正则表达式的语言里，正则表达式的语法都是一�?.. 阅读全文

草原上的骆驼 2011-03-04 16:06 发表评论

Python Beautiful Soup

草原上的骆驼 — Fri, 04 Mar 2011 08:05:00 GMT

Beautiful Soup 中文文档

http://www.crummy.com/software/BeautifulSoup/documentation.zh.html#Using%20tag%20names%20as%20members

http://www.meegoq.com/forum.php?mod=viewthread&tid=63&extra=

http://edu.codepub.com/2010/0208/20340.php

http://www.crummy.com/software/BeautifulSoup/documentation.zh.html

草原上的骆驼 2011-03-04 16:05 发表评论

Python UUID

草原上的骆驼 — Fri, 04 Mar 2011 08:03:00 GMT

UUID objects (universally unique identifiers) according to RFC 4122.
UUID objects (universally unique identifiers) according to RFC 4122.

This module provides immutable UUID objects (class UUID) and the functions
uuid1(), uuid3(), uuid4(), uuid5() for generating version 1, 3, 4, and 5
UUIDs as specified in RFC 4122.

If all you want is a unique ID, you should probably call uuid1() or uuid4().
Note that uuid1() may compromise privacy since it creates a UUID containing
the computer's network address.  uuid4() creates a random UUID.

Typical usage:

    >>> import uuid

    # make a UUID based on the host ID and current time
    >>> uuid.uuid1()
    UUID('a8098c1a-f86e-11da-bd1a-00112444be1e')

    # make a UUID using an MD5 hash of a namespace UUID and a name
    >>> uuid.uuid3(uuid.NAMESPACE_DNS, 'python.org')
    UUID('6fa459ea-ee8a-3ca4-894e-db77e160355e')

    # make a random UUID
    >>> uuid.uuid4()
    UUID('16fd2706-8baf-433b-82eb-8c7fada847da')

    # make a UUID using a SHA-1 hash of a namespace UUID and a name
    >>> uuid.uuid5(uuid.NAMESPACE_DNS, 'python.org')
    UUID('886313e1-3b8a-5372-9b90-0c9aee199e5d')

    # make a UUID from a string of hex digits (braces and hyphens ignored)
    >>> x = uuid.UUID('{00010203-0405-0607-0809-0a0b0c0d0e0f}')

    # convert a UUID to a string of hex digits in standard form
    >>> str(x)
    '00010203-0405-0607-0809-0a0b0c0d0e0f'

    # get the raw 16 bytes of the UUID
    >>> x.bytes
    '\x00\x01\x02\x03\x04\x05\x06\x07\x08\t \x0b\x0c \x0e\x0f'

    # make a UUID from a 16-byte string
    >>> uuid.UUID(bytes=x.bytes)
    UUID('00010203-0405-0607-0809-0a0b0c0d0e0f')

This module works with Python 2.3 or higher.

草原上的骆驼 2011-03-04 16:03 发表评论

Python Urllib2

草原上的骆驼 — Fri, 04 Mar 2011 08:02:00 GMT

http://docs.python.org/library/urllib.html

讄��时旉��

import socket

import urllib2

socket.setdefaulttimeout(seconds)

open = urllib2.urlopen("

�q�socket.setdefaulttimeout() 讄��了全局默认��时旉��Q�从而给urllibe2.urlopen()也设�|�了默认的超时时�?br />

抓取囄��(�q�个例子里的Request找不刎ͼ�我一般只有urllib2)
soup=urlllib2.open(url)

# Let's create a function that downloads a file, and saves it locally.
# This function accepts a file name, a read/write mode(binary or text),
# and the base url.

def stealStuff(file_name,file_mode,base_url):
    from urllib2 import Request, urlopen, URLError, HTTPError

    #create the url and the request
    url = base_url + file_name
    req = Request(url)

    # Open the url
    try:
        f = urlopen(req)
        print "downloading " + url

        # Open our local file for writing
        local_file = open(file_name, "w" + file_mode)
        #Write to our local file
        local_file.write(f.read())
        local_file.close()

    #handle errors
    except HTTPError, e:
        print "HTTP Error:",e.code , url
    except URLError, e:
        print "URL Error:",e.reason , url

# Set the range of images to 1-50.It says 51 because the
# range function never gets to the endpoint.
image_range = range(1,51)

# Iterate over image range
for index in image_range:

    base_url = 'http://www.techniqal.com/'
    #create file name based on known pattern
    file_name =  str(index) + ".jpg"
    # Now download the image. If these were text files,
    # or other ascii types, just pass an empty string
    # for the second param ala stealStuff(file_name,'',base_url)
    stealStuff(file_name,"b",base_url)

草原上的骆驼 2011-03-04 16:02 发表评论

Python String

草原上的骆驼 — Fri, 04 Mar 2011 07:52:00 GMT

Python-String-Function

字符串中字符大小写的变换�Q?/strong>

    * S.lower()   #��写
    * S.upper()   #大写
    * S.swapcase()   #大小写互�?br />     * S.capitalize()   #首字母大�?br />     * String.capwords(S)
      #�q�是模块中的�Ҏ��。它把S用split()函数分开�Q�然后用capitalize()把首字母变成大写�Q�最后用join()合�ƈ��C��?br />     * S.title()    #只有首字母大写，其余为小写，模块中没有这个方�?

字符串在输出时的寚w��Q?

    * S.ljust(width,[fillchar])
      #输出width个字�W�，S左对齐，不��部分用fillchar填充�Q�默认的为空根{�?br />     * S.rjust(width,[fillchar])    #叛_��?br />     * S.center(width, [fillchar])    #中间寚w��
    * S.zfill(width)   #把S变成width长，�q�在叛_��齐，不��部分�?补��

字符串中的搜索和替换�Q?/strong>

    * S.find(substr, [start, [end]])
      #�q�回S中出现substr的第一个字母的标号�Q�如果S中没有substr则返�?1。start和end作用��q��当于在S[start:end]中搜�?br />     * S.index(substr, [start, [end]])
      #与find()相同�Q�只是在S中没有substr�Ӟ��会返回一个运行时错误
    * S.rfind(substr, [start, [end]])
      #�q�回S中最后出现的substr的第一个字母的标号�Q�如果S中没有substr则返�?1�Q�也��是说从双��v的第一�ơ出现的substr的首字母标号
    * S.rindex(substr, [start, [end]])
    * S.count(substr, [start, [end]])    #计算substr在S中出现的�ơ数
    * S.replace(oldstr, newstr, [count])
      #把S中的oldstar替换为newstr�Q�count为替换次数。这是替换的通用形式�Q�还有一些函数进行特�D�字�W�的替换
    * S.strip([chars])
      #把S中前后chars中有的字�W�全部去掉，可以理解为把S前后chars替换为None
    * S.lstrip([chars])
    * S.rstrip([chars])
    * S.expandtabs([tabsize])
      #把S中的tab字符替换没空��|��每个tab替换为tabsize个空��|��默认�?�?

字符串的分割和组合：

    * S.split([sep, [maxsplit]])
      #以sep为分隔符�Q�把S分成一个list。maxsplit表示分割的次数。默认的分割�W��ؓ�I�白字符
    * S.rsplit([sep, [maxsplit]])
    * S.splitlines([keepends])
      #把S按照行分割符分�ؓ一个list�Q�keepends是一个bool��|��如果为真每行后而会保留行分割符�?br />     * S.join(seq) #把seq代表的序列──字符串序列，用S�q�接��h��

字符串的mapping�Q�这一功能包含两个函数�Q?/strong>

    * String.maketrans(from, to)
      #�q�回一�?56个字�W�组成的��译表，其中from中的字符被一一对应地�{换成to�Q�所以from和to必须是等长的�?br />     * S.translate(table[,deletechars])
      #使用上面的函��C�后的��译表，把S�q�行��译�Q��ƈ把deletechars中有的字�W�删掉。需要注意的是，如果S为unicode字符�Ԍ��那么��׃��支持 deletechars参数�Q�可以��用把某个字符��译为None的方式实现相同的功能。此外还可以使用codecs模块的功能来创徏更加功能强大的翻译表�?

字符串还有一对编码和解码的函敎ͼ�

    * S.encode([encoding,[errors]])
      #其中encoding可以有多�U��|��比如gb2312 gbk gb18030 bz2 zlib big5 bzse64�{�都支持。errors默认��gؓ"strict"�Q�意思是UnicodeError。可能的��D��?ignore', 'replace', 'xmlcharrefreplace', 'backslashreplace' 和所有的通过codecs.register_error注册的倹{��这一部分内容涉及codecs模块�Q�不是特明白
    * S.decode([encoding,[errors]])

字符串的��试函数�Q�这一�c�d��数在string模块中没有，�q�些函数�q�回的都是bool��|��

    * S.startwith(prefix[,start[,end]])
      #是否以prefix开�?br />     * S.endwith(suffix[,start[,end]])
      #以suffix�l�尾
    * S.isalnum()
      #是否全是字母和数字，�q�至��有一个字�W?br />     * S.isalpha() #是否全是字母�Q��ƈ臛_��有一个字�W?br />     * S.isdigit() #是否全是数字�Q��ƈ臛_��有一个字�W?br />     * S.isspace() #是否全是�I�白字符�Q��ƈ臛_��有一个字�W?br />     * S.islower() #S中的字母是否全是��写
    * S.isupper() #S中的字母是否便是大写
    * S.istitle() #S是否是首字母大写�?

字符串类型�{换函敎ͼ��q�几个函数只在string模块中有�Q?/strong>

    * string.atoi(s[,base])
      #base默认�?0�Q�如果�ؓ0,那么s��可以是012�?x23�q�种形式的字�W�串�Q�如果是16那么s��只能是0x23�?X12�q�种形式的字�W�串
    * string.atol(s[,base]) #转成long
    * string.atof(s[,base]) #转成float

*******************************************************************************************************************
Python字符串在输出时的寚w��Q?/p>

S.ljust(width,[fillchar])

#输出width个字�W�，S左对齐，不��部分用fillchar填充�Q�默认的为空根{�?/p>

S.rjust(width,[fillchar]) #

叛_��?/p>

S.center(width, [fillchar]) #

中间寚w�� S.zfill(width) #把S变成width长，�q�在叛_��齐，不��部分�?补��字符串中的搜索和替换�Q?/p>

S.find(substr, [start, [end]])

#�q�回S中出现substr的第一个字母的标号�Q�如果S中没有substr则返�?1。start和end作用��q��当于在S[start:end]中搜�?/p>

S.index(substr, [start, [end]])

#与find()相同�Q�只是在S中没有substr�Ӟ��会返回一个运行时错误

S.rfind(substr, [start, [end]])

#�q�回S中最后出现的substr的第一个字母的标号�Q�如果S中没有substr则返�?1�Q�也��是说从双��v的第一�ơ出现的substr的首字母标号

S.rindex(substr, [start, [end]])
S.count(substr, [start, [end]]) #

计算substr在S中出现的�ơ数

S.replace(oldstr, newstr, [count])

#把S中的oldstar替换为newstr�Q�count为替换次数。这是替换的通用形式�Q�还有一些函数进行特�D�字�W�的替换

**************************************************************************************************

草原上的骆驼 2011-03-04 15:52 发表评论

天天av综合,在线一级成人,一区二区三区日韩

python 判断 null

Python �q�接 Mysql

python的time和date处理

Python IO

1.open

2.��L���?/span>

��L��本文�?/h4> input = open('data', 'r') #�W�二个参数默认�ؓr input = open('data')

��M���q�制文�g

��d��所有内�?/h4> file_object = open('thefile.txt') try: all_the_text = file_object.read( ) finally: file_object.close( )

��d��定字�?/h4> file_object = open('abinfile', 'rb') try: while True: chunk = file_object.read(100) if not chunk: break do_something_with(chunk) finally: file_object.close( )

��L���?/h4> list_of_all_the_lines = file_object.readlines( ) 如果文�g是文本文�Ӟ���q�可以直接遍历文件对象获取每行： for line in file_object: process line

3.写文�?/span>

写文本文�?/h4> output = open('data', 'w')

写二�q�制文�g

�q�加写文�?/h4> output = open('data', 'w+')

写数�?/h4> file_object = open('thefile.txt', 'w') file_object.write(all_the_text) file_object.close( )

写入多行

Python Mysql

What is MySQLdb?

How do I install the MySQLdb?

Database Connection:

Example:

Creating Database Table:

Example:

INSERT Operation:

Example:

Example:

READ Operation:

Example:

Update Operation:

Example:

DELETE Operation:

Example:

Performing Transactions:

Example:

COMMIT Operation:

ROLLBACK Operation:

Disconnecting Database:

Handling Errors:

python 中文��q��

Python Beautiful Soup

Beautiful Soup 中文文档

Python UUID

Python Urllib2

Python String

2.��L��?/span>

��L��本文�?/h4>
input = open('data', 'r')
#�W�二个参数默认�ؓr
input = open('data')

��M��q�制文�g

��d��所有内�?/h4>
file_object = open('thefile.txt')
try:
all_the_text = file_object.read( )
finally:
file_object.close( )

��d��定字�?/h4>
file_object = open('abinfile', 'rb')
try:
while True:
chunk = file_object.read(100)
if not chunk:
break
do_something_with(chunk)
finally:
file_object.close( )

��L��?/h4>
list_of_all_the_lines = file_object.readlines( )

如果文�g是文本文�Ӟ��q�可以直接遍历文件对象获取每行：

for line in file_object:
process line

写文本文�?/h4>
output = open('data', 'w')

�q�加写文�?/h4>
output = open('data', 'w+')

写数�?/h4>
file_object = open('thefile.txt', 'w')
file_object.write(all_the_text)
file_object.close( )