title: How to replace a string in a list of strings in a DataFrame (Python)?
body: <p>I have a Dataframe which consists of lists of lists in two seperate columns.</p>
  
  <pre><code>import pandas as pd
  data = pd.DataFrame()
  data["Website"] = [["google.com", "amazon.com"], ["google.com"], ["aol.com", "no website"]]
  data["App"] = [["Ok Google", "Alexa"], ["Ok Google"], ["AOL App", "Generic Device"]]
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/BZa7G.png" rel="nofollow noreferrer">Thats how the Dataframe looks like</a></p>
  
  <p>I need to replace certain strings in the first column (here: "no website") with the according string in the second column (here: "Generic Device"). The replacing string has the same index in the list as the string that needs to be replaced.</p>
  
  <p><strong>What did not work so far:</strong>
  I tried several forms of <em>str.replace(x,y)</em> for lists and DataFrames and nothing worked. A simple <em>replace(x,y)</em> does not work as I need to replace several different strings. I think I can't get my head around the indexing thing.
  I already googled and stackoverflowed for two hours and haven't found a solution yet.</p>
  
  <p>Many thanks in advance! Sorry for bad engrish or noob mistakes, I am still learning.</p>
  
  <p>-Max</p>