title: why pandas raise "KeyError: True" while "df.Apples==30 & True" is not a key too?
body: <p>Based on official pandas documentations and help on:</p>
  
  <pre><code>pandas.DataFrame.loc
  </code></pre>
  
  <p>the loc allows to access a group of rows and columns by label(s) or a Boolean array.
  (<a href="https://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.loc.html" rel="nofollow noreferrer">https://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.loc.html</a>)</p>
  
  <p>but it look a Boolean array does not work really!</p>
  
  <pre><code>import pandas as pd
  
  data=[[30, 21],[0, 121],[4, 121]]
  df= pd.DataFrame(data, columns=['Apples', 'Bananas'])
  
  print(df.loc[df.Apples==30 &amp; True])      # It's OK
  print(df.loc[True])                      # **doesn't work**
  </code></pre>