Go language Regular Expressions-practice tutorials

The library used by the regular expression processing

regexp

Use to RegExp library functions have mustcompile and Compile

MustCompile 的作用和 Compile 一样,    将正则表达式编译成一个正则对象（使用 PERL 语法）。该正则对象会采用“leftmost-first”模式。选择第一个匹配结果.如果正则表达式语法错误，则返回错误信息。不同的是，当正则表达式 str 不合法时，MustCompile 会抛出异常,而 Compile 仅返回一个 error 值

FindString

返回匹配上正则表达式最左边的一个字符串，如果没有匹配上会返回空字符串

Example 1 Get Company (corporate name), address, telephone (phone) in the following text

         <ul class="t3">                   <li class="company">山东东阿阿胶股份有限公司</li>              <li class="address">山东省东阿县阿胶街78号</li>               <li class="telephone">0635-3262315</li>    </ul>

Regular expressions

        <li class="company">(.+)</li>        <li class="company">(.+)</li>        <li class="telephone">(.+)</li>

Code implementation

    Package ... import (...)    "RegExp" ...) ... var (company = RegExp. Mustcompile (' <li class= ' Company ' > (. +) </li> ') address = RegExp. Mustcompile (' <li class= ' address > (. +) </li> ') telephone = RegExp. Mustcompile (' <li class= ' telephone > (. +) </li> ') var (respbody = ' <ul cl ass= "T3" > <li class= "Company" > Shandong Donga Gelatin Co., Ltd. </li> <li class= "address "> No. 78th, Qian, Shandong Province, China </li> <li class=" Telephone ">0635-3262315</li> </ul > ') companymatches: = Company. FindString (respbody) Companyrst: = Strings. Trimspace (Strings. Trim (Strings. Trim (companymatches, ' <li class= ' Company > '), ' </') addressmatches: = Address. FindString (respbody) Addressrst: = Strings. Trimspace (Strings. Trim (Strings. Trim (addressmatches, ' <li class= ' address ' > '), ' </') telephOnematches: = telephone. FindString (respbody) Telephonerst: = Strings. Trimspace (Strings. Trim (Strings. Trim (telephonematches, ' <li class= ' telephone ' > '), ' </')

Explain:

其中正则表达式   `<li class="company">(.+)</li>`  的意思是匹配以<li class="company">开头，以</li>结尾，中间匹配一次或多次除换行符之外的任何字符‘.‘ 匹配除换行符（\n、\r）之外的任何单个字符。要匹配包括 ‘\n‘ 在内的任何字符，请使用像"(.|\n)"的模式。‘+‘ 匹配前面的子表达式一次或多次。例如，‘zo+‘ 能匹配 "zo" 以及 "zoo"，但不能匹配 "z"。+ 等价于 {1,}。

Example 2 converting HTML tags all to lowercase

re, _ := regexp.Compile("\\<[\\S\\s]+?\\>")或者    re, _ = regexp.Compile(`\<[\S\s]+?\>`)respBody = re.ReplaceAllStringFunc(respBody, strings.ToLower)

Explain:

    匹配以‘<‘开头，以’\>‘结尾，中间匹配一个或多个任意字符，而且尽可能少的匹配所搜索到的字符，因为?标示非贪婪模式    举个例子：            正则表达式`\<[\S\s]+?\>处理下面字符串 ’<test1\> nice<test2\>‘，返回结果’<test1\>‘            而正则表达式`\<[\S\s]+\>处理下面字符串 ’<test1\> nice<test2\>‘，返回接’<test1\> nice<test2\>‘？当该字符紧跟在任何一个其他限制符 (*, +, ?, {n}, {n,}, {n,m}) 后面时，匹配模式是非贪婪的。非贪婪模式尽可能少的匹配所搜索的字符串，而默认的贪婪模式则尽可能多的匹配所搜索的字符串。例如，对于字符串 "oooo"，‘o+?‘ 将匹配单个 "o"，而 ‘o+‘ 将匹配所有 ‘o‘。\s  匹配任何空白字符，包括空格、制表符、换页符等等。等价于 [ \f\n\r\t\v]。\S  匹配任何非空白字符。等价于 [^ \f\n\r\t\v]。

Example 3 Remove Style

re, _ = regexp.Compile("\\<style[\\S\\s]+?\\</style\\>")或者    re, _ = regexp.Compile(`\<style[\S\s]+?\</style\>`)respBody = re.ReplaceAllString(respBody, "")

Explain:
same Example 2

Example 4 removing script

re, _ = regexp.Compile("\\<script[\\S\\s]+?\\</script\\>") 或者    re, _ = regexp.Compile(`\<script[\S\s]+?\</script\>`)respBody = re.ReplaceAllString(respBody, "")

Explain:
same Example 3

Example 5 removing all the HTML code within the angle brackets and replacing them with line breaks

re, _ = regexp.Compile("\\<[\\S\\s]+?\\>")respBody = re.ReplaceAllString(respBody, "\n")

Explain:
same Example 3

Example 6 removing a continuous line break

re, _ = regexp.Compile("\\s{1,}")respBody = re.ReplaceAllString(respBody, "\n")  

Explain:

{n,}  n 是一个非负整数。至少匹配n 次。例如，‘o{2,}‘ 不能匹配 "Bob" 中的 ‘o‘，但能匹配 "foooood" 中的所有 o。‘o{1,}‘ 等价于 ‘o+‘。‘o{0,}‘ 则等价于 ‘o*‘。

Example 7 find below last number 15

<a  target=‘_self‘ href=‘/search/不孕症-p15/‘ class=‘last‘>尾页</a>

Code:

allPage       = regexp.MustCompile(`<a  target=‘_self‘ href=‘/search/[.\x{4e00}-\x{9fa5}0-9]+-p[0-9]/‘[ ]*class=‘last‘>尾页</a>`)allPagePrefix = regexp.MustCompile(`<a  target=‘_self‘ href=‘/search/[.\x{4e00}-\x{9fa5}0-9]+-p`)allPageSuffix = regexp.MustCompile(`/‘[ ]*class=‘last‘>\x{5c3e}\x{9875}</a>`)numPage = allPage.FindString(body)numPage = allPagePrefix.ReplaceAllString(numPage, "")numPage = allPageSuffix.ReplaceAllString(numPage, "")

Match details:
Regular expression <a target= ' _self ' href= '/search/[.\x{4e00}-\x{9fa5}0-9]+-p[0-9]/' []*class= ' last ' > End </a>:

    匹配以"<a  target=‘_self‘ href=‘/search/"开头，以class=‘last‘>尾页</a>结尾，中间匹配若干个除换行外的任意字符或者中文字符    简易爬虫实战项目代码路径：https://github.com/KenmyZhang/medicine-manual-spider

Go language Regular Expressions-practice tutorials