title: pandas: concat multiple dataframes while not ignoring the indexes python
body: <p>I've three dataframes:</p>
  
  <pre><code>df2 = pd.DataFrame(np.random.randint(0, 50, (3,3)), columns = ["A", "B", "C"], index = ["1", "2", "3"])
  df3 = pd.DataFrame(np.random.randint(0, 50, (4,2)), columns = ["D", "E"], index = ["100", "101", "102", "103"])
  df4 = pd.DataFrame(np.random.randint(0, 1000, (11,5)), columns = ["F", "G", "H", "I", "J"], index = ["1", "2", "3", "4", "5", "6", "7", "100", "101", "102", "103"])
  </code></pre>
  
  <p>and I want to concat these dataframes in </p>
  
  <pre><code>df5 = pd.DataFrame(columns = ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J"])
  </code></pre>
  
  <p>Now while using </p>
  
  <pre><code>df5 = pd.concat([df5, df2])
  df5 = pd.concat([df5, df3])
  df5 = pd.concat([df5, df4])
  </code></pre>
  
  <p>it creates multiple 1, 2, 3, 4, 100, 101, 102, and 103 indexes. I don't want it to do that. Ideally, I want value for FGHIJ to be pasted in first index 1 and likewise for index 2, 3, 4, 100, 101, 102, 103. Can anyone please help?</p>
  
  <p><a href="https://i.stack.imgur.com/aBt93.jpg" rel="nofollow noreferrer">OutputDataframe</a></p>