怎么使用Python中的正则表达式处理html文件

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使用Python中的正则表达式处理html文件

finditer方法是一种全匹配方法。您可能已经使用了findall方法，它返回多个匹配字符串的列表。finditer返回一个迭代器顺序地为多个匹配中的每一个生成匹配对象。在下面的代码中，这些匹配对象被访问（通过for循环），因此可以打印组1。

您的任务是编写Python RE来识别HTML文本文件中的某些模式。将代码添加到STARTER脚本为这些模式编译RE（将它们分配给有意义的变量名称），并将这些RE应用于文件的每一行，打印出找到的匹配项。

1.编写识别HTML标签的模式，然后将其打印为“TAG:TAG string”（例如“TAG:b”代表标签）。为了简单起见，假设左括号和右括号每个标记的（<，>）将始终出现在同一行文本中。第一次尝试可能使regex“<.*>”其中“.”是与任何字符匹配的预定义字符类符号。尝试找出这一点，找出为什么这不是一个好的解决方案。编写一个更好的解决方案，解决这个问题

2.修改代码，使其区分开头和结尾标记（例如p与/p)打印OPENTAG和CLOSETAG

import sys, re
#------------------------------
testRE = re.compile('(logic|sicstus)', re.I)
testI = re.compile('<[A-Za-z]>', re.I)
testO = re.compile('<[^/](S*?)[^>]*>')
testC = re.compile('</(S*?)[^>]*>')
with open('RGX_DATA.html') as infs: 
    linenum = 0
    for line in infs:
        linenum += 1
        if line.strip() == '':
            continue
        print('  ', '-' * 100, '[%d]' % linenum, '
   TEXT:', line, end='')
    
        m = testRE.search(line)
        if m:
            print('** TEST-RE:', m.group(1))
        mm = testRE.finditer(line)
        for m in mm:
            print('** TEST-RE:', m.group(1))
        
        index= testI.finditer(line)
        for i in index:
           print('Tag:',i.group().replace('<', '').replace('>', ''))
           
        open1= testO.finditer(line)
        for m in open1:
           print('opening:',m.group().replace('<', '').replace('>', ''))
           
        close1= testC.finditer(line)
        for n in close1:
           print('closing:',n.group().replace('<', '').replace('>', ''))

请注意，有些HTML标签有参数，例如：

<table border=1 cellspacing=0 cellpadding=8>

确保打开标记的模式适用于带参数和不带参数的标记，即成功找到并打印标签标签。现在扩展您的代码，以便打印两个打开的标签标签和参数，例如:

OPENTAG: table
PARAM: border=1
PARAM: cellspacing=0
PARAM: cellpadding=8

 		open1= testO.finditer(line)
        for m in open1:
            #print('opening:',m.group().replace('<', '').replace('>', ''))
            firstm= m.group().replace('<', '').replace('>', '').split()
            num = 0
            for otherm in firstm:
                if num == 0:
                    print('opening:',otherm)
                else:
                    print('pram:',otherm)
                num+= 1

在正则表达式中，可以使用反向引用来指示匹配早期部分的子字符串,应再次出现正则表达式的。格式为N（其中N为正整数），并返回到第N个匹配的文本正则表达式组。例如，正则表达式，如：r" (w+) 1 仅当与组（w+）完全匹配的字符串再次出现时才匹配 backref1出现的位置。这可能与字符串“踢”匹配.例如，“the”出现两次。使用反向引用编写一个模式，当一行包含成对的open和关闭标签，例如在粗体中.

考虑到我们可能想要创建一个执行HTML剥离的脚本，即一个HTML文件，并返回一个纯文本文件，所有HTML标记都已从中删除出来这里我们不打算这样做，而是考虑一个更简单的例子，即删除我们在输入数据文件的任何行中找到的HTML标记。

你应该能够让您已经定义的RE识别HTML标签这样做,将生成的文本打印到屏幕上为STRIPPED：。。

import sys, re
#------------------------------
# PART 1: 
   # Key thing is to avoid matching strings that include
   # multiple tags, e.g. treating '<p><b>' as a single
   # tag. Can do this in several ways. Firstly, use
   # non-greedy matching, so get shortest possible match
   # including the two angle brackets:
tag = re.compile('</?(.*?)>') 
   # The above treats the '/' of a close tag as a separate
   # optional component - so that this doesn't turn up as
   # part of the match '.group(1)', which is meant to return
   # the tag label. 
   # Following alternative solution uses a negated character
   # class to explicitly prevent this including '>': 
tag = re.compile('</?([^>]+)>') 
   # Finally, following version separates finding the tag
   # label string from any (optional) parameters that might
   # also appear before the close angle bracket:
tag = re.compile(r'</?(w+)([^>]+)?>') 
   # Note that use of '' (as word boundary anchor) here means
   # we must mark the regex string as a 'raw' string (r'..'). 
#------------------------------
# PART 2: 
   # Following closeTag definition requires first first char
   # after the open angle bracket to be '/', while openTag
   # definition excludes this by requiring first char to be
   # a 'word char' (w):
openTag  = re.compile(r'<(w[^>]*)>')
closeTag = re.compile(r'</([^>]*)>')
   # Following revised definitions are more carefully stated
   # for correct extraction of tag label (separately from
   # any parameters:
openTag  = re.compile(r'<(w+)([^>]+)?>')
closeTag = re.compile(r'</(w+)s*>')
#------------------------------
# PART 3: 
   # Above openTag definition will already get the string
   # encompassing any parameters, and return it as
   # m.group(2), i.e. defn: 
openTag  = re.compile(r'<(w+)([^>]+)?>')
   # If assume that parameters are continuous non-whitespace
   # chars separated by whitespace chars, then we can divide
   # them up using split - and that's how we handle them
   # here. (In reality, parameter strings can be a lot more
   # messy than this, but we won't try to deal with that.)
#------------------------------
# PART 4: 
openCloseTagPair = re.compile(r'<(w+)([^>]+)?>(.*?)</1s*>')
   # Note use of non-greedy matching for the text falling
   # *between* the open/close tag pair - to avoid false
   # results where have two similar tag pairs on same line.
#------------------------------
# PART 5: URLS
   # This is quite tricky. The URL expressions in the file
   # are of two kinds, of which the first is a string
   # between double quotes ("..") which may include
   # whitespace. For this case we might have a regex: 
url = re.compile('href="https://www.19jp.com">

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