During web scraping sometimes an expected element is not present. This recently happened during a web scraping project when the client input data was not correct causing the page to load with an error and didn’t have the expected data to scrape. The web scraping was being done in Excel using Selenium and Chrome browser. The error handling can be done a couple of different ways. I used the approach of assigning a webelement object to the expected element and then test if the object is Nothing.
Element Test Code
' class that has distance in miles
Set miClass = driver.FindElementByClass("mi", timeout:=0, Raise:=False)
If Not miClass Is Nothing Then
{Element Present}
Else
{ Element not Present, Error Handling}This project required loading almost 20,000 web pages. Sometimes the web page url failed to load. Although not directly tied to testing for the present of an element this error case still needed to be handled. For this case Excel VBA error handing is used. Multiple attempts are made to load the url. If the web page loads then the “attempt loop” is exited early. If the maximum number of attempts is reached, then error handling is used.
In an Excel VBA, On Error is used to control the error handing. Before making the web page loading attempt On Error GoTo and Exit For are used to manage the multiple attempts.
Web Page Loading Error handling
' attempt to get website
On Error GoTo tryAgain ' if error GoTo tryAgain
For try = 1 To Attempts ' number of attempts to try (const)
' get website
driver.Get url ' attempt to load web page, if error GoTo tryAgain
Exit For ' web page loaded exit For
tryAgain:
Next try ' next attempt
On Error GoTo 0 ' reset Error handling to stop on error
If (try <> (Attempts + 1)) Then ' Test if maximum attempts were reached
{Page Loaded, Do Stuff}
Else
{Page Didn't Load, Error Handling Stuff}