python正则表达式应⽤优化实例
1、问题出现
需要提取⼀份xml⽂件中参数名和参数值，格式如下：
<p name="actOlLaPdcch">true</p>
我们需要的字段如上，红⾊部分为参数名，蓝⾊部分为参数值，当然，实际⽂档中还有很多⼲扰因素。
步骤为先打开⽂件，然后⽤正则表达式匹配到我们需要的母项（r"<managedObject class=\"LNCEL\""），然后开始匹配。
期间发⽣了⼀个问题，调试的时候我使⽤的⼀⼩段样本如下：
<managedObject class="LNCEL" distName="MRBTS-421961/LNBTS-421961/LNCEL-1" operation="create" version="TL16A">
<p name="a1TimeToTriggerDeactInterMeas">480ms</p>
<p name="a2RedirectQci1">disabled</p>
<p name="a2TimeToTriggerActGERANMeas">320ms</p>
<p name="a2TimeToTriggerActInterFreqMeas">480ms</p>
<p name="a2TimeToTriggerRedirect">1024ms</p>
<p name="a3Offset">6</p>
使⽤的正则表达式为：
p1 = r"((?<=\")\w+(?=\"))" #p1为查的参数名正则表达式
p2 = r"(?<=\>)\w+(?=\<)" #p2为查的参数值正则表达式
pattern1 = repile(p1)
pattern2 = repile(p2)
get =pattern1.findall(line)[0]
get2=pattern2.findall(line)[0]
lncel1_pa.append(get)
lncel1_va.append(get2)
调试过程是完全正常的，匹配数字和⽂字即可，也是没问题的，然⽽在真正运⾏打开整个⽂档过程中出现了如下报错：
1 File "E:/pgtool/Files/filesprocess.py", line 32, in <module>
2 get2=pattern2.findall(line)[0]
3
4 IndexError: list index out of range
也就意味着在提取参数值过程中list[0]都已经超出了范围，也就是这个list是空的，这是哪⾥出了问题呢？
经过spyder的debug功能调试，逐⾏运⾏，终于发现了问题所在，即在提取参数中我们使⽤的是 r"(?<=\>)\w+(?=\<)" 正则表达式也就是提取例如<p name="eutraCelId">108</p> ⼤于号⼩于号之间的⽂字
和数字（此处得到的值为108）。但某些参数值存在空格，⽽且空格类型不⽌⼀种，有1个空格的，也有多个空格间隔的，如下：
<p name="dlsOldtcTarget">6 db</p>
<p name="dlsUsePartPrb">PRBs with PSS or SSS and PBCH used</p>
以⾄于出现了正则表达式匹配不到。
2、根据此问题做的优化
考虑到有空格存在所以进⾏了第⼀次正则表达式改进：\w+ ?
p2 = r"(?<=\>)\w+(?=\<)"#p2为查的参数值正则表达式
修改为-->
p2 = r"(?<=\>)\w+ ?(?=\<)"#p2为查的参数值正则表达式
但这种优化对 <p name="dlsOldtcTarget">6 db</p>这类有⼀个空格或者没有空格的才能匹配，对于<p name="dlsUsePartPrb">PRBs with PSS or SSS and PBCH used</p>还是不能匹配（间隔多个空格类
型），于是进⾏了第⼆次优化，将匹配参数值的正则表达式改为.*，也就是在⼤于号与⼩于号之间的参数值匹配为任意值（除换⾏外），问题彻底解决。
p2 = r"(?<=\>)\w+(?=\<)"#p2为查的参数值正则表达式
修改为-->
p2 = r"(?<=\>).*(?=\<)"#p2为查的参数值正则表达式
3、进⼀步优化
当然，为了避免出现两⾏重叠问题⽽带来的贪婪匹配问题，我们需要在.*后添加⼀个？号来避免贪婪匹配
p2 = r"(?<=\>)\w+(?=\<)"#p2为查的参数值正则表达式
修改为-->
p2 = r"(?<=\>).*?(?=\<)"#p2为查的参数值正则表达式，避免贪婪匹配带来的结果增加⼀个？
⽬前完整的代码也仅仅只能匹配⼀个LNCEL下的参数，后续我们将进⼀步编辑，可提取其他LNCEL下
的参数，⼤致的思路为：为各个LNCEL参数提取后都放置到⼀个DataFrame中，然后再进⾏⽔平联结，最后转⼊excel中。
4、完整代码如下
代码：
# -*- coding: utf-8 -*-
"""
Created on Thu Jul 12 15:19:37 2018
@author: lishuixing_nok
"""
import re
import numpy as np
import pandas as pd
fp=open('l')
adline()
#print (line)
lncel1_pa=[]
lncel1_va=[]
lncel2=[]
lncel3=[]
cels=[]
while line:
if re.match(r"<managedObject class=\"LNCEL\"",line):
k=re.search(r"(LNBTS-)(\d+)(/LNCEL)(-\d+)",line).group(2)+re.search(r"(LNBTS-)(\d+)(/LNCEL)(-\d+)",line).group(4)
cels.append(k)
elif (re.match(r"</managedObject>",line)):
break
else:
if re.match(r"<p name=",line):
p1 = r"((?<=\")\w+(?=\"))"
p2 = r"(?<=\>).*?(?=\<)"
pattern1 = repile(p1)
pattern2 = repile(p2)
get =pattern1.findall(line)[0]
get2=pattern2.findall(line)[0]
lncel1_pa.append(get)
lncel1_va.append(get2)
else:pass
line = fp.readline()
fp.close()
#print (lncel1_pa,'\n',lncel1_va) 打印参数和
pd1=pd.DataFrame(lncel1_va,index=lncel1_pa,columns=cels)
pd1.index.name='parameter'
print (pd1)
<_excel(r'E:\pgtool\Files\lncelvalue.xlsx',sheet_name='lncel')
提取⽂档样本：
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<raml xmlns="raml21.xsd" version="2.1">
<cmData id="3221225472" scope="all" type="plan">
<header>
<log action="create" appInfo="" appVersion="" dateTime="2018-07-09T09:50:29" user=""/>
<log action="create" appInfo="" appVersion="" dateTime="2018-07-09T09:55:00" user=""/>
<log action="create" appInfo="" appVersion="" dateTime="2018-07-09T10:15:18" user=""/>
<log action="create" appInfo="" appVersion="" dateTime="2018-07-09T10:27:07" user=""/>
<log action="create" appInfo="" appVersion="" dateTime="2018-07-09T11:15:18" user=""/>
<log action="create" appInfo="" appVersion="" dateTime="2018-07-09T11:56:23" user=""/>
<log action="create" appInfo="" appVersion="" dateTime="2018-07-09T12:15:18" user=""/>
<log action="create" appInfo="" appVersion="" dateTime="2018-07-09T13:05:55" user=""/>
<log action="create" appInfo="" appVersion="" dateTime="2018-07-09T16:15:18" user=""/>
<log action="create" appInfo="" appVersion="" dateTime="2018-07-09T16:17:01" user=""/>
<log action="create" appInfo="" appVersion="" dateTime="2018-07-09T16:21:01" user=""/>
<managedObject class="LNCEL" distName="MRBTS-421961/LNBTS-421961/LNCEL-1" operation="create" version="TL16A">
<p name="a1TimeToTriggerDeactInterMeas">480ms</p>
<p name="a2RedirectQci1">disabled</p>
<p name="a2TimeToTriggerActGERANMeas">320ms</p>
<p name="a2TimeToTriggerActInterFreqMeas">480ms</p>
<p name="a2TimeToTriggerRedirect">1024ms</p>
<p name="a3Offset">6</p>
<p name="a3ReportInterval">640ms</p>
<p name="a3TimeToTrigger">320ms</p>
<p name="a5ReportInterval">640ms</p>
<p name="a5TimeToTrigger">640ms</p>
<p name="cqiPerSbCycK">1</p>
<p name="cqiPerSimulAck">false</p>
<p name="csgType">openAccess</p>
<p name="dSrTransMax">64n</p>
<p name="dlsOldtcTarget">98</p>
<p name="dlsUsePartPrb">PRBs with PSS or SSS and PBCH used</p> <p name="eUlLaAtbPeriod">30</p>
<p name="eUlLaBlerAveWin">30</p>
<p name="eUlLaDeltaMcs">3</p>
<p name="eUlLaLowMcsThr">1</p>
<p name="eUlLaLowPrbThr">1</p>
<p name="eUlLaPrbIncDecFactor">16</p>
<p name="enableAmcPdcch">true</p>
<p name="filterCoefficientRSRQ">fc4</p>
<p name="filterCoefficientRSSI">fc2</p>
<p name="gbrCongHandling">l2andl3</p>
<p name="grpAssigPUSCH">0</p>正则化解决过拟合
<p name="harqMaxMsg3">4</p>
<p name="harqMaxTrDl">5</p>
<p name="harqMaxTrUlTtiBundling">8</p>
<p name="harqMaxTxUl">7</p>
<p name="hopModePusch">interSubFrame</p>
<p name="hysA3Offset">0</p>
<p name="hysThreshold2GERAN">2</p>
<p name="hysThreshold2InterFreq">0</p>
<p name="hysThreshold2Wcdma">0</p>
<p name="hysThreshold2a">0</p>
<p name="hysThreshold3">0</p>
<p name="hysThreshold4">0</p>
<p name="idleLBPercCaUe">0</p>
<p name="idleLBPercentageOfUes">0</p>
<p name="ilReacTimerUl">50</p>
<p name="inactivityTimer">10</p>
<p name="iniMcsDl">6</p>
<p name="lbLoadFilCoeff">4</p>
<p name="lcrId">1</p>
<p name="ulsSchedMethod">channel aware</p>
<list name="dFListPucch">
<item>
<p name="dFpucchF1">0</p>
<p name="dFpucchF1b">3</p>
<p name="dFpucchF2">1</p>
<p name="dFpucchF2a">2</p>
<p name="dFpucchF2b">2</p>
</item>
</list>
<list name="drxProfile102">
<item>
<p name="drxInactivityT">2560</p>
<p name="drxLongCycle">1280ms</p>
<p name="drxOnDuratT">10</p>
<p name="drxProfileIndex">102</p>
<p name="drxProfilePriority">30</p>
<p name="drxRetransT">16</p>
</item>
</list>
<list name="drxProfile103">
<item>
<p name="drxInactivityT">10</p>
<p name="drxLongCycle">160ms</p>
<p name="drxOnDuratT">6</p>
<p name="drxProfileIndex">103</p>
<p name="drxProfilePriority">30</p>
<p name="drxRetransT">16</p>
</item>
</list>
<list name="mimoClConfig">
<item>
<p name="mimoClCqiThD">70</p>
<p name="mimoClCqiThU">90</p>
<p name="mimoClRiThD">28</p>
<p name="mimoClRiThU">32</p>
</item>
</list>
<list name="mimoOlConfig">
<item>
<p name="mimoOlCqiThD">50</p>
<p name="mimoOlCqiThU">60</p>
<p name="mimoOlRiThD">20</p>
<p name="mimoOlRiThU">21</p>
</item>
</list>
<list name="qci1eVTTConfig">
<item>
<p name="qci1DlTargetBler">30</p>
<p name="qci1HarqMaxTrDl">5</p>
<p name="qci1HarqMaxTrUl">5</p>
<p name="qci1ReconStopTimer">10</p> <p name="qci1ThroughputFactorDl">16</p> <p name="qci1ThroughputFactorUl">16</p> <p name="qci1UlTargetBler">3</p>
</item>
</list>
<list name="ulpcPucchConfig">
<item>
<p name="ulpcLowlevCch">-103</p>
<p name="ulpcLowqualCch">1</p>
<p name="ulpcUplevCch">-98</p>
<p name="ulpcUpqualCch">4</p>
</item>
</list>
<list name="ulpcPuschConfig">
<item>
<p name="ulpcLowlevSch">-103</p>
<p name="ulpcLowqualSch">18</p>
<p name="ulpcUplevSch">-96</p>
<p name="ulpcUpqualSch">20</p>
</item>
</list>
<list name="antCablingMappingConfig">
<item>
<p name="rruPort1AntId">0</p>
<p name="rruPort2AntId">1</p>
<p name="rruPort3AntId">2</p>
<p name="rruPort4AntId">3</p>
<p name="rruPort5AntId">4</p>
<p name="rruPort6AntId">5</p>
<p name="rruPort7AntId">6</p>
<p name="rruPort8AntId">7</p>
</item>
</list>
<list name="drxProfile101">
<item>
<p name="drxRetransT">4</p>
<p name="drxInactivityT">10</p>
<p name="drxLongCycle">40ms</p>
<p name="drxOnDuratT">6</p>
<p name="drxProfileIndex">101</p>
<p name="drxProfilePriority">30</p>
</item>
</list>
<list name="furtherPlmnIdL">
<item>
<p name="autoRemovalAllowed">false</p>
<p name="cellReserve">Not Reserved</p>
<p name="mcc">460</p>
<p name="mnc">29</p>
<p name="mncLength">2</p>
</item>
</list>
<list name="redBwRbUlConfig">
<item>
<p name="redBwMaxRbUl">100</p>
<p name="redBwMinRbUl">1</p>
</item>
</list>
<list name="srsDlMimoModeDepConf">
<item>
<p name="beamformingType">nonBeamforming</p> <p name="srsBandwidth">2hbw</p>
<p name="srsUePeriodicity">40ms</p>
</item>
</list>
<list name="tmSwitchThresholdDef">
<item>
<p name="tm3to7CqiTh">40</p>
<p name="tm8to3CqiTh">70</p>
<p name="tm9to3CqiTh">150</p>
</item>
</list>
</managedObject>
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