title: How to parallel loop two sets of columns in pandas df?
body: <p>Is there a way to parallel loop two lists of columns in pandas df? For example, I need to create C1=A1 + B2, C2=A2+B2, C3=A3+B3...</p>
  <pre><code>df = pd.DataFrame(np.random.randn(3, 6),
             columns=['A1', 'A2', 'A3','B1', 'B2','B3'])
  
      A1          A2          A3          B1          B2          B3
  0   -0.045858   0.627827    -1.562130   2.094783    0.654119    -0.996711
  1   1.003585    0.735500    0.795338    -0.803864   -0.071655   -0.514118
  2   0.083501    0.774820    -1.477767   -1.260052   0.861952    -0.674270
  </code></pre>