title: Concatenate lists from df column
body: <p>I have a data frame that looks like this:</p>
  
  <pre><code>import pandas as pd
  df = pd.DataFrame({'id': [1,2,3], 'tokens': [["anna","brings","work","life"], ["apples","bananas"], ["sun","trial","once"]]})
  </code></pre>
  
  <p>what I am trying to do is simply concatenate all the strings from lists in the column into a single list so that the resulting list looks like this:</p>
  
  <pre><code>result_list = ["anna","brings","work","life", "apples","bananas","sun","trial","once"]
  </code></pre>
  
  <p>I have tried to iterate over each row and then each element in a list:</p>
  
  <pre><code>result_list = [item for sublist in df.tokens for item in sublist]
  </code></pre>
  
  <p>but what I get is a list every single symbol of lists.
  What am I missing?</p>