python读写二进制文件的方法
本文实例讲述了python读写二进制文件的方法。分享给大家供大家参考。具体如下：
初学python，现在要读一个二进制文件，查找doc只发现 file提供了一个read和write函数，而且读写的都是字符串，如果只是读写char等一个字节的还行，要想读写如int,double等多字节数 据就不方便了。在网上查到一篇贴子，使用struct模块里面的pack和unpack函数进行读写。下面就自己写代码验证一下。

接着再将其读进来   
>>> file = open(r"c:/debug.txt", "rb")
>>> (a,b,c) = unpack("idh",file.read(8+8+2))
>>> a,b,c
(12345, 67.890000000000001, 15)
>>> print a,b,c
12345 67.89 15
>>> file.close()

在操作过程中需要注意数据的size

注意  wb,rb中的b字，一定不可以少

方法1：   
myfile=open('c:\\t','rb')
s=myfile.read(1)
byte=ord(s) #将一个字节 读成一个数
print hex(byte) #转换成16进制的字符串

方法2   
import struct
myfile=open('c:\\t','rb').read(1)
print struct.unpack('c',myfile)
print struct.unpack('b',myfile)

写入

To open a file for binary writing is easy, it is the same way you do for reading, just change the mode into “wb”.
file = open("test.bin","wb")
But, how to write the binary byte into the file?
You may write it straight away with hex code like this:
file.write("\x5F\x9D\x3E") file.close()
Now, check it out with hexedit,
hexedit test.bin
You will see this:
00000000 5F 9D 3E _.> 00000020 00000040
Now, open the file to append more bytes:
file = open("test.bin","ab")
What if I want to store by bin value into a stream and write it one short?
s ="\x45\xF3" s = s + "%c%c" % (0x45,0xF3) file.write(s) file.close()
Any convenient ways if I can obtained a hex string, and want to convert it back to binary format?
Yes, you just need to import binascii
import binascii hs="5B7F888489FEDA" hb=binascii.a2b_hex(hs) file.write(hb) file.close()
希望本文所述对大家的Python程序设计有所帮助。

Python正则表达式使用经典实例
本文给大家总结了17种python正则表达式使用经典实例，非常不错具有参考借鉴价值，下面列出Python正则表达式的几种匹配用法，具体内容如下所示：

1.测试正则表达式是否匹配字符串的全部或部分
regex=ur"" #正则表达式
if re.search(regex, subject):
do_something()
else:
do_anotherthing()

2.测试正则表达式是否匹配整个字符串   
regex=ur"\Z" #正则表达式末尾以\Z结束
if re.match(regex, subject):
    do_something()
else:
    do_anotherthing()

3.创建一个匹配对象，然后通过该对象获得匹配细节(Create an object with details about how the regex matches (part of) a string)   
regex=ur"" #正则表达式
match = re.search(regex, subject)
if match:
    # match start: match.start()
    # match end (exclusive): atch.end()
    # matched text: match.group()
    do_something()
else:
    do_anotherthing()

4.获取正则表达式所匹配的子串(Get the part of a string matched by the regex)   
regex=ur"" #正则表达式
match = re.search(regex, subject)
if match:
    result = match.group()
else:
    result = ""

5. 获取捕获组所匹配的子串(Get the part of a string matched by a capturing group)   
regex=ur"" #正则表达式
match = re.search(regex, subject)
if match:
    result = match.group(1)
else:
    result = ""

6. 获取有名组所匹配的子串(Get the part of a string matched by a named group)   
regex=ur"" #正则表达式
match = re.search(regex, subject)
if match:
result = match.group"groupname")
else:
result = ""

7. 将字符串中所有匹配的子串放入数组中(Get an array of all regex matches in a string)   
result = re.findall(regex, subject)

8.遍历所有匹配的子串(Iterate over all matches in a string)   
for match in re.finditer(r"<(.*?)\s*.*?/\1>", subject)
    # match start: match.start()
    # match end (exclusive): atch.end()
    # matched text: match.group()

9.通过正则表达式字符串创建一个正则表达式对象(Create an object to use the same regex for many operations)   
reobj = re.compile(regex)

10.用法１的正则表达式对象版本（use regex object for if/else branch whether (part of) a string can be matched）   
reobj = re.compile(regex)
if reobj.search(subject):
    do_something()
else:
    do_anotherthing()

11.用法２的正则表达式对象版本（use regex object for if/else branch whether a string can be matched entirely）
   
reobj = re.compile(r"\Z")　＃正则表达式末尾以\Z 结束
if reobj.match(subject):
    do_something()
else:
    do_anotherthing()

12.创建一个正则表达式对象，然后通过该对象获得匹配细节（Create an object with details about how the regex object matches (part of) a string）   
reobj = re.compile(regex)
match = reobj.search(subject)
if match:
    # match start: match.start()
    # match end (exclusive): atch.end()
    # matched text: match.group()
    do_something()
else:
    do_anotherthing()

13.用正则表达式对象获取匹配子串（Use regex object to get the part of a string matched by the regex）   
reobj = re.compile(regex)
match = reobj.search(subject)
if match:
    result = match.group()
else:
    result = ""

14.用正则表达式对象获取捕获组所匹配的子串（Use regex object to get the part of a string matched by a capturing group）   
reobj = re.compile(regex)
match = reobj.search(subject)
if match:
    result = match.group(1)
else:
    result = ""

15.用正则表达式对象获取有名组所匹配的子串（Use regex object to get the part of a string matched by a named group）   
reobj = re.compile(regex)
match = reobj.search(subject)
if match:
    result = match.group("groupname")
else:
    result = ""

16.用正则表达式对象获取所有匹配子串并放入数组（Use regex object to get an array of all regex matches in a string）   
reobj = re.compile(regex)
result = reobj.findall(subject)

17.通过正则表达式对象遍历所有匹配子串（Use regex object to iterate over all matches in a string）   
reobj = re.compile(regex)
for match in reobj.finditer(subject):
    # match start: match.start()
    # match end (exclusive): match.end()
    # matched text: match.group()

字符串替换

1.替换所有匹配的子串   
#用newstring替换subject中所有与正则表达式regex匹配的子串
result = re.sub(regex, newstring, subject)

2.替换所有匹配的子串（使用正则表达式对象）   
reobj = re.compile(regex)
result = reobj.sub(newstring, subject)

字符串拆分

1.字符串拆分   
result = re.split(regex, subject)

2.字符串拆分（使用正则表示式对象）   
reobj = re.compile(regex)
result = reobj.split(subject)