处理 RSelenium 错误消息 [英] Handle RSelenium error messages

问题描述

目前正在抓取一个页面，该页面可能包含可变数量的元素，有时还会使用不同的选择器格式化相同的数据元素.目前正在尝试使用一些 tryCatch 代码忽略 RSelenium 抛出的错误，但当指定的元素不在页面上时仍会停止:

Currently scraping a page which can have a variable amount of elements and also sometimes formats the same data elements with different selectors. Currently trying to ignore errors thrown by RSelenium with some tryCatch code but still stops when the specified element is not on the page:

  result <- tryCatch({
    webElem <- remDr$findElement('xpath', "//tr[(((count(preceding-sibling::*) + 1) = 9) and parent::*)]//span[(((count(preceding-sibling::*) + 1) = 1) and parent::*)]")
  }, warning = function(cond) {
    rank1_US <- NA
  }, 
  error = function(cond) {
    rank1_US <- NA
  }, finally = {
    rank1_US <- webElem$getElementText() %>% unlist(.) %>% ifelse(length(.) == 0, NA, .)
  })

当在页面上找不到特定元素时会出错:

Which runs into an error when the particular element can't be found on the page:

Selenium message:Unable to locate element: //tr[(((count(preceding-sibling::*) + 1) = 9) and parent::*)]//span[(((count(preceding-sibling::*) + 1) = 1) and parent::*)]
For documentation on this error, please visit: http://seleniumhq.org/exceptions/no_such_element.html
Build info: version: '3.0.1', revision: '1969d75', time: '2016-10-18 09:48:19 -0700'
System info: host: '462a81a34fb2', ip: '172.17.0.2', os.name: 'Linux', os.arch: 'amd64', os.version: '4.4.39-boot2docker', java.version: '1.8.0_111'
Driver info: org.openqa.selenium.firefox.FirefoxDriver
Capabilities [{rotatable=false, raisesAccessibilityExceptions=false, firefoxOptions={args=[], profile=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... <truncated>
Session ID: c7f538b9-b516-411d-ace9-a980353ae442
*** Element info: {Using=xpath, value=//tr[(((count(preceding-sibling::*) + 1) = 9) and parent::*)]//span[(((count(preceding-sibling::*) + 1) = 1) and parent::*)]}

有人有办法处理这个错误吗?

Anyone have a way to handle the error?

推荐答案

您可以尝试以下操作:

result <- tryCatch({
    suppressMessages({
      webElem <- remDr$findElement('xpath', "//tr[(((count(preceding-sibling::*) + 1) = 9) and parent::*)]//span[(((count(preceding-sibling::*) + 1) = 1) and parent::*)]")
      rank1_US <- webElem$getElementText() %>% unlist(.) %>% ifelse(length(.) == 0, NA, .)
      rank1_US
    })
  }, 
  error = function(e) {
    NA_character_
  }
)

这篇关于处理 RSelenium 错误消息的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！