R 使用Xpath从HTML代码中提取注释

我试图找出以下HTML代码片段的注释中所写的内容，这只是该代码的一部分：

<table id="datalist1" cellspacing="0" border="0" style="border-width:1px;border-style:solid;width:100%;border-collapse:collapse;">
<tr>
    <td style="font-size:7pt;">
                                            <table width="100%" border="0" cellspacing="0" cellpadding="0">
                                                <tr align="left">
                                                    <td width="50%" class="subhead1">
                                                        <!-- <b>IE CODE : 0514026049</b> --> ' I want text inside this comment

                                                    </td>
                                                    <td rowspan="9" valign="top">
                                                        <span id="datalist1_ctl00_lbl_p"></span>
                                                    </td>
                                                </tr>

我正在尝试以下方法

1获取元素的Xpath

2阅读网页

3转到“注释”节点

4在注释中提取文本

  library(rvest)
  library(xml2)

  url <- 'http://agriexchange.apeda.gov.in/ExportersDirectory/exporters_list.aspx?letter=Z'
  webpage <- read_html(url)
    ' Xpath of comment element I want to grab
    //*[@id="datalist1"]/tbody/tr[1]/td/table/tbody/tr[1]/td[1]/comment()



  webpage %>% 
      html_nodes(xpath='//*[@id="datalist1"]/tbody/tr[1]/td/table/tbody/tr[1]/td[1]/comment()')%>%html_text()
#character(0) ' this is output

但是上面的代码给出了一个空字符串。因为我从未使用过Xpath，所以我不知道这是否是正确的方法

我必须对所有的注释元素运行这个。

---

简言之，我想我的问题是如何在HTML代码中提取注释？

这可能会帮助您：

webpage %>% 
html_nodes(xpath='//*[@id="datalist1"]') %>%  
          extract2(1) %>% html_nodes("tr") %>%  
          extract2(1) %>% html_nodes("td") %>% 
          extract2(2) %>% html_nodes(xpath = '//comment()') %>% extract2(15) %>%  html_text()

---

尝试从XPath/table/tbody/tr[1]->/table//tr[1]中删除tbody，因为它可以通过浏览器添加到DOM中……现在您正在寻找XPath解决方案，您可能需要再次检查：是！当我检查站点的源代码时，tbody不在那里。我将尝试在不使用tbodyd的情况下使用它。您是只希望HTML文档中的所有注释，还是有特定的规则来指定您想要的注释？很难从你的例子中分辨出来。我想要所有带有标签的评论

library(rvest)
library(tidyverse)

pg <- read_html("http://agriexchange.apeda.gov.in/ExportersDirectory/exporters_list.aspx?letter=Z")

html_nodes(pg, xpath=".//comment()[contains(., 'IE CODE')]/../../..") %>% # target the comment then back up to the table
  map_df(~{

    # extract the <td> (column 1)
    html_nodes(.x, xpath=".//td[1]") %>% 
      html_text(trim=TRUE) %>% 
      str_replace_all("[[:space:]]+", " ") -> tmp

    # add in the comment to the "missing" <td> value
    html_node(.x, xpath=".//comment()") %>% 
      html_text() %>% 
      stri_replace_all_regex("<b>|</b>", "") -> tmp[1]

    # set it up for data frame-ing
    set_names(as.list(tmp), sprintf("X%s", 1:8))

  })
## # A tibble: 196 x 8
##                        X1                      X2                                                                           X3
##                     <chr>                   <chr>                                                                        <chr>
##  1  IE CODE : 0514026049           Z A M PRODUCTS                                          54 DAROOD GRAN SHAHPEER GATE MEERUT
##  2  IE CODE : AQDPV0923E                Z CONNECT             H-302, AIRFORCE NAVAL, ATHIPALAYAM PIRIVU, GANAPATHY, COIMBATORE
##  3  IE CODE : 2912000459        Z K INTERNATIONAL                           MUGHALPURA IST NEAR ISMAIL BEG KI MASJID MORADABAD
##  4  IE CODE : 0307069753  Z K R INTERNATIONAL CO.            4084, PLAZA SHOPPING CENTRE,104/142, SHERIF DEVJI STREET, MUMBAI,
##  5  IE CODE : 3117507531          Z S ENTERPRISES  SURVEY NO 12,PLOT NO.64,FLAT NO 1, KAUSARBAUGH NIBM ROAD KONDHWA KHURD PUNE
##  6  IE CODE : 0500009503               Z. EXPORTS                                 T-283, NEAR GURUDWARA BHAIJI B AHATA KIDARA,
##  7  IE CODE : 0713030658        Z. K. MANGO MANDI                              APMC YARD, RMC CHANNAPATNA, RAMANAGARA DISTRICT
##  8  IE CODE : 0599037351             Z.A. CRAFTS,                      A-56, GALI NO. 6, CHOUHAN BANGER, NEW SEELAM PUR, DELHI
##  9  IE CODE : 0609001353        Z.B.INTERNATIONAL 1ST FLOOR,25TH MILE STONE,AGRA MATHURA ROAD,VILL CHUMURA, POST-FARAH MATHURA
## 10  IE CODE : 0501009256             Z.D. EXPORTS             J-51, EXTENSION, STREET NO. 12/3, RAMESH PARK, LAXMI NAGAR DELHI
## # ... with 186 more rows, and 5 more variables: X4 <chr>, X5 <chr>, X6 <chr>, X7 <chr>, X8 <chr>