title: using pandas isin with groupby
body: <p>I have a dataframe the looks like the following below. I want to be able to find out the  total number of "missing" that is occurring in the dataframe but to also group the data by columns A,B and C.</p>
  
  <pre><code>               A   B           C        D        E        F  total_missing
  0     Miami Heat  FL  Basketball       21  MISSING  MISSING             11
  1     Miami Heat  FL  Basketball       17  MISSING  MISSING             11
  2     Miami Heat  FL  Basketball  MISSING       12       23             11
  3  Orlando Magic  FL  Basketball  MISSING        5  MISSING             11
  4  Orlando Magic  FL  Basketball       10  MISSING  MISSING             11
  5  Orlando Magic  FL  Basketball        5  MISSING  MISSING             11
  </code></pre>
  
  <p>This code below only gives back the total number of the words missing which is 11 and it appears in all the rows. I just want the total 11 to appear in one cell and to be able to group it by columns a,b and c which I am not sure how to do with the isin function. Any help would be appreciated.</p>
  
  <pre><code>import pandas as pd
  df = pd.read_excel(r'C:\ds_test\basketball.xlsx')
  df['total_missing'] = df.isin(["MISSING"]).sum().sum()
  print(df['total_missing'])
  
  
  
  </code></pre>