title: 'Wrong number of items passed 2, placement implies 1' error with pandas dataframe by operating two columns
body: <p>I have dataframe - for the purpose of sample data every day has only 10 minutes:</p>
  <pre><code>                Date    Close
  0   2019-06-20 07:00:00 2927.25
  1   2019-06-20 07:05:00 2927.00
  2   2019-06-20 07:10:00 2926.75
  183 2019-06-21 07:00:00 2932.25
  184 2019-06-21 07:05:00 2932.25
  185 2019-06-21 07:10:00 2931.00
  366 2019-06-24 07:00:00 2941.75
  367 2019-06-24 07:05:00 2942.25
  368 2019-06-24 07:10:00 2941.50
  549 2019-06-25 07:00:00 2925.50
  550 2019-06-25 07:05:00 2926.50
  551 2019-06-25 07:10:00 2926.50
  732 2019-06-26 07:00:00 2903.25
  </code></pre>
  <p>I want to get the daily range of the closing price.<br>
  I grouped the data by day and get the min max of close:</p>
  <pre><code>rangeofday = df.groupby(pd.Grouper(key='Date', freq='1D')).agg({'Close':[np.min, np.max]})
  rangeofday = rangeofday.dropna()
  
              Close
              amin    amax
  Date        
  2019-06-20  2926.75 2927.25
  2019-06-21  2931.00 2932.25
  2019-06-24  2941.50 2942.25
  2019-06-25  2925.50 2926.50
  2019-06-26  2903.25 2904.00
  ... ... ...
  </code></pre>
  <p>So far so good, but what happens is that the names of the columns are weird, and somehow not accessible by name.<br></p>
  <pre><code>    rangeofday.amin
  or
      rangeofday.Closeamin
  
      = 'DataFrame' object has no attribute 'amin'
  </code></pre>
  <p>So I can access them with iloc:</p>
  <pre><code>rangeofday.iloc[:, [1]]
  
              Close
              amax
  Date    
  2019-06-20  2927.25
  2019-06-21  2932.25
  2019-06-24  2942.25
  2019-06-25  2926.50
  </code></pre>
  <p>Now I try to subtract min from max:</p>
  <pre><code>rangeofday['range'] = (rangeofday.iloc[:, [0]] - rangeofday.iloc[:, [1]])/0.25
  </code></pre>
  <p>and get the error:</p>
  <pre><code>Wrong number of items passed 2, placement implies 1
  </code></pre>
  <p>What does this mean and how can get around this error?</p>