title: Pandas: Fast way to get cols/rows containing na
body: <p>In Pandas we can drop cols/rows by <code>.dropna(how = ..., axis = ...)</code> but is there a way to get an array-like of True/False indicators for each col/row, which would indicate whether a col/row contains <em>na</em> according to <code>how</code> and <code>axis</code> arguments?</p>
  <p>I.e. is there a way to convert <code>.dropna(how = ..., axis = ...)</code> to a method, which would instead of actual removal just <em>tell</em> us, which cols/rows <em>would</em> be removed if we called <code>.dropna(...)</code> with specific <code>how</code> and <code>axis</code>.</p>
  <p>Thank you for your time!</p>