title: set value in dataframe
body: <p>I have this list of tuples where I can find in first position one index and in second position the value corresponding.</p>
  <p>here an example :</p>
  <pre><code>list_val = [ [(0, 0.9), (451, 0.5)] , [(10, 0.5), (52, 0.2)] ]
  an_other_list = [10, 1000, 1002, 1003, ...] # the real index i want
  </code></pre>
  <p>in a pandas data frame, I want to set values like this:</p>
  <pre><code>index = []
  for i in list_val:
      index.append(an_other_list[list_val.index(i)])
  
  df = pd.DataFrame()
  
  for i in list_val:
      for j in i:
  
          df.set_value( an_other_list[j[0]], an_other_list[list_val.index(i)], j[1])
  </code></pre>
  <p>but this is too slow and I know it's not optimized.</p>
  <p>How can I improve this ?</p>
  <p>EDIT:</p>
  <p>here an output example where all the value are not set yet  :</p>
  <p><a href="https://i.stack.imgur.com/WfvJv.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/WfvJv.png" alt="enter image description here" /></a></p>
  <p>I ran this example on a simple dataframe without setting the index as the list &quot;index&quot;.</p>
  <p>Sorry if it's not enough clear</p>