title: Pandas KeyError: value not in index
body: <p>I have the following code, </p>
  
  <pre><code>df = pd.read_csv(CsvFileName)
  
  p = df.pivot_table(index=['Hour'], columns='DOW', values='Changes', aggfunc=np.mean).round(0)
  p.fillna(0, inplace=True)
  
  p[["1Sun", "2Mon", "3Tue", "4Wed", "5Thu", "6Fri", "7Sat"]] = p[["1Sun", "2Mon", "3Tue", "4Wed", "5Thu", "6Fri", "7Sat"]].astype(int)
  </code></pre>
  
  <p>It has always been working until the csv file doesn't have enough coverage (of all week days). For e.g., with the following .csv file, </p>
  
  <pre><code>DOW,Hour,Changes
  4Wed,01,237
  3Tue,07,2533
  1Sun,01,240
  3Tue,12,4407
  1Sun,09,2204
  1Sun,01,240
  1Sun,01,241
  1Sun,01,241
  3Tue,11,662
  4Wed,01,4
  2Mon,18,4737
  1Sun,15,240
  2Mon,02,4
  6Fri,01,1
  1Sun,01,240
  2Mon,19,2300
  2Mon,19,2532
  </code></pre>
  
  <p>I'll get the following error:</p>
  
  <pre><code>KeyError: "['5Thu' '7Sat'] not in index"
  </code></pre>
  
  <p>It seems to have a very easy fix, but I'm just too new to Python to know how to fix it.</p>