title: Combine 2 Boolean columns in pandas
body: <p>I  have a <strong>table</strong> with few flag columns.(3 agencies rated bank; all cases mutually exclusive => at one time only one flag was ON. If flag1 has a value, flag2 and flag3 wont have any value and so on)</p>
  
  <pre><code>  BankName     Flag1       Flag2    Flag3  
      B1         TRUE         
      B2                                FALSE
      B3                      TRUE
      B4          FALSE  
      B5                       TRUE 
  </code></pre>
  
  <p>and so on.</p>
  
  <p>What I want:</p>
  
  <pre><code>  BankName     Flag1       Flag2    Flag3   Anyflag  
      B1         TRUE                           TRUE 
      B2                               FALSE    FALSE
      B3                      TRUE              TRUE
      B4          FALSE                         FALSE   
      B5                       TRUE             TRUE
  </code></pre>
  
  <p>Basically I wish to combine the flags overall in a separate column. I have tried <strong>merge, concat and they dont seem to work on boolean columns.</strong></p>
  
  <p>Tried:</p>
  
  <pre><code>[IN]:
  df['Any flag']=pd.concat(df['Flag1'], df['Flag2'], df['Flag3'])
  [OUT]
  TypeError: first argument must be an iterable of pandas objects, you 
  passed an object of type "Series"
  [IN]:
  df['Any flag']=pd.concat(df['Flag1'], df['Flag2'], df['Flag3'], axis=0)
  [OUT]
  TypeError: concat() got multiple values for argument 'axis'
  </code></pre>
  
  <p>Please help.</p>