因为最近工作中，需要设计根据wirshark截获的报文自动产生测试case的小工具，我重温了python。这个笔记，就是根据这个工具的实现，来记录python语法的学习过程。
这个工具的功能如下图所示，其中wirshark cap可以通过wirshark自身的功能导出为pmsl格式，也就是一种XML，同时公司使用的case script也是一种XML，只是添加了一些循环，判断等功能。
所以这个工具涉及文件操作，XML解析和一些python的基本语法功能
一、PYTHON 基本语法概念
1.什么是main函数
if __name__ == "__main__":上面这个就是python的main函数的声明
2. 变量申明
python对变量申明不像那么严格，但也不像shell那么随便。一般变量通过首次赋值产生，当超出作用范围时自动消亡。这几句话的意思是，变量如果要使用就一定要先给他赋值。比如
print str1Traceback (most recent call last):
File "<pyshell#0>", line 1, in <module>
print str1
NameError: name 'str1' is not defined所以一定要先赋值
str1 = 'hello'
print str1
python一样有全局变量和局部变量的概念。
3. python 常用的变量类型
数值型
value = 12string
str1 = 'hello'str1 = "hello"这里有个双引号还是单引号的问题，我的理解是除非设计转义字符，两者都是一样的。
a = 'let\'s us'
a = "let's us"list
也就是C语言中的数组
a = ['spam', 'eggs', 100, 1234]a[0]
a[1]Dictionary
大家称呼这个味字典型，其实可以类比为C语言中的结构体。因为python里面是没有struct这类东西的，当然python可以用class的方法替代struct。但Dictionary这个类型也可以在某些时候当做struct这个概念来用
d = {"server":"mpilgrim", "database":"master"}
这个类型是可以作为不同类型数据的container的，但要注意一个问题dictionary在插入的时候是乱序的，也就是说当我做
d["newdata"]='fda'4.Python的层次结构
python依靠代码缩进和：来确定代码的前后层次关系
如下面这个函数，缩进起到了C语言中{}的作用。
def GetEnumName(attribename,valuestr):
"""
@author: limim
@param attribename:attribname
@type attribename:str
@param valuestr:mmt log value
@type valuestr:str
@return:the enum name
@rtype:str
"""
tree = ReadFromXml('PegasusEnumMapping.xml')
root = tree.getroot()
value = str(int(valuestr,16))
errorret = ''
for listnode in root.iter('attrib'):
strlist = listnode.attrib['name'].split('.')
attriblist = attribename.split('.')
substrlist = strlist[(len(strlist)-4):]
subattriblist = attriblist[(len(attriblist)-4):]
if substrlist == subattriblist:
for enumlistnode in listnode:
if enumlistnode[0].text == value:
return enumlistnode[1].text
else:
errorret = enumlistnode[1].text
print "error"
print attribename
print 'mmt log value' + ' ' + valuestr
print 'set default value' + ' ' + errorret
print '##############'
return errorret二、elementTree
这个工具处理的主要文件格式是XML，就用elementTree这个库来处理，下面是要处理文件格式的一部分。
<?xml version="1.0"?>
<pdml version="0" creator="wireshark/1.20.0.1">
<packet>
<proto name="geninfo" pos="0" showname="General information" size="98">
<field name="num" pos="0" show="1246" showname="Number" value="4de" size="98"/>
<field name="len" pos="0" show="98" showname="Frame Length" value="62" size="98"/>
<field name="caplen" pos="0" show="98" showname="Captured Length" value="62" size="98"/>
<field name="timestamp" pos="0" show="Mar 6, 2013 18:28:28.729395000 China Standard Time" showname="Captured Time" value="1362565708.729395000" size="98"/>
</proto>
<proto name="frame" showname="Frame 1246: 98 bytes on wire (784 bits), 98 bytes captured (784 bits)" size="98" pos="0">
<field name="frame.time" showname="Arrival Time: Mar 6, 2013 18:28:28.729395000 China Standard Time" size="0" pos="0" show="Mar 6, 2013 18:28:28.729395000"/>
<field name="frame.time_epoch" showname="Epoch Time: 1362565708.729395000 seconds" size="0" pos="0" show="1362565708.729395000"/>
<field name="frame.time_delta" showname="Time delta from previous captured frame: 0.000475000 seconds" size="0" pos="0" show="0.000475000"/>
<field name="frame.time_delta_displayed" showname="Time delta from previous displayed frame: 0.000000000 seconds" size="0" pos="0" show="0.000000000"/>
<field name="frame.time_relative" showname="Time since reference or first frame: 93.072253000 seconds" size="0" pos="0" show="93.072253000"/>
<field name="frame.number" showname="Frame Number: 1246" size="0" pos="0" show="1246"/>
<field name="frame.len" showname="Frame Length: 98 bytes (784 bits)" size="0" pos="0" show="98"/>
<field name="frame.cap_len" showname="Capture Length: 98 bytes (784 bits)" size="0" pos="0" show="98"/>
<field name="frame.marked" showname="Frame is marked: False" size="0" pos="0" show="0"/>
<field name="frame.ignored" showname="Frame is ignored: False" size="0" pos="0" show="0"/>
<field name="frame.protocols" showname="Protocols in frame: eth:ip:udp:mmtss:sicap" size="0" pos="0" show="eth:ip:udp:mmtss:sicap"/>
<field name="frame.coloring_rule.name" showname="Coloring Rule Name: SICAP" size="0" pos="0" show="SICAP"/>
<field name="frame.coloring_rule.string" showname="Coloring Rule String: sicap" size="0" pos="0" show="sicap"/>
</proto>
<proto name="eth" showname="Ethernet II, Src: 192.168.254.1 (00:0f:bb:69:93:ee), Dst: DCT-INF (00:10:18:cb:b5:fd)" size="14" pos="0">
<field name="eth.dst" showname="Destination: DCT-INF (00:10:18:cb:b5:fd)" size="6" pos="0" show="00:10:18:cb:b5:fd" value="001018cbb5fd">
<field name="eth.addr" showname="Address: DCT-INF (00:10:18:cb:b5:fd)" size="6" pos="0" show="00:10:18:cb:b5:fd" value="001018cbb5fd"/>
<field name="eth.ig" showname=".... ...0 .... .... .... .... = IG bit: Individual address (unicast)" size="3" pos="0" show="0" value="0" unmaskedvalue="001018"/>
<field name="eth.lg" showname=".... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)" size="3" pos="0" show="0" value="0" unmaskedvalue="001018"/>
</field>
<field name="eth.src" showname="Source: 192.168.254.1 (00:0f:bb:69:93:ee)" size="6" pos="6" show="00:0f:bb:69:93:ee" value="000fbb6993ee">
<field name="eth.addr" showname="Address: 192.168.254.1 (00:0f:bb:69:93:ee)" size="6" pos="6" show="00:0f:bb:69:93:ee" value="000fbb6993ee"/>
<field name="eth.ig" showname=".... ...0 .... .... .... .... = IG bit: Individual address (unicast)" size="3" pos="6" show="0" value="0" unmaskedvalue="000fbb"/>
<field name="eth.lg" showname=".... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)" size="3" pos="6" show="0" value="0" unmaskedvalue="000fbb"/>
</field>
<field name="eth.type" showname="Type: IP (0x0800)" size="2" pos="12" show="0x0800" value="0800"/>
</proto>1. 文件读取
from xml.etree.ElementTree import ElementTree, Element
import sys
def ReadFromXml(path):
''''read from xml and prase it
author:limin
path: the file path
return ElementTree'''
tree = ElementTree()
tree.parse(path);
return tree通过
tree = ElementTree()
tree.parse(path);
在调试模式下，可以看到tree就是根据读入的XML文件用不同层级的NODE构成的结构体。这个时候操作就很方便了，我们可以先拿到root，在遍历整个tree就可以方便的读取XML中任意一个节点的attrib，text，tag这些内容。
def ReadPacketContent(tree,framenum):
'''
read the packet content
node:the xml node
num: the index of the node
'''
SicCapMessage = []
root = tree.getroot() #check the boundary
num = 0
flag = 0
for node in root: # proto level node
if flag == 1:
break
num = num + 1
#print protonode.tag,protonode.attrib
for protonode in node:
if protonode.attrib['name'] == 'frame':
frameList = parseFrameHead(protonode)
if frameList[1] != str(framenum):
break
else:
SicCapMessage.insert(0,frameList)
print "find the frame, number is" + frameList[1]
flag = 1
print num
print len(root)
if num == 0 or num > len(root) - 1:
print "can not find the frame num"
return SicCapMessage
for protonode in root[num - 1]:
if protonode.attrib['name'] == 'sicap':
#dictPrint(parseSiCapMessage(protonode))
SicCapMessage.extend(parseSiCapMessage(protonode))
return SicCapMessage可以看到
protonode.attrib
2.文件写入
读取的问题解决了，剩下的就是写入了。只用调用
tree.write('test.xml','UTF-8')
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