title: Why does referencing a concatenated pandas dataframe return multiple entries?
body: <p>When I create a dataframe using concat like this:</p>
  
  <pre><code>import pandas as pd
  dfa = pd.DataFrame({'a':[1],'b':[2]})
  dfb = pd.DataFrame({'a':[3],'b':[4]})
  dfc = pd.concat([dfa,dfb])
  </code></pre>
  
  <p>And I try to reference like I would for any other DataFrame I get the following result:</p>
  
  <pre><code>&gt;&gt;&gt; dfc['a'][0]
  0    1
  0    3
  Name: a, dtype: int64
  </code></pre>
  
  <p>I would expect my concatenated DataFrame to behave like a normal DataFrame and return the integer that I want like this simple DataFrame does:</p>
  
  <pre><code>&gt;&gt;&gt; dfa['a'][0]
  1
  </code></pre>
  
  <p>I am just a beginner, is there a simple explanation for why the same call is returning an entire DataFrame and not the single entry that I want? Or, even better, an easy way to get my concatenated DataFrame to respond like a normal DataFrame when I try to reference it? Or should I be using something other than concat?</p>