title: Python: clear existing string in search box using selenium
body: <p>I am using webdriver to login into a website at the moment. There is a table search which already have a digit "50" in it. I want to change it to "300".</p>
  
  <p>Code snippet:</p>
  
  <pre><code>no="300"
  blank = driver.find_element_by_id("PC1_PageSize")
  blank.send_keys(no)
  </code></pre>
  
  <p>But when I tried this, it became "50300". My expected result is to replace "50" to "300". Thanks in advance!</p>