title: Get the mean across multiple Pandas DataFrames
body: <p>I'm generating a number of dataframes with the same shape, and I want to compare them to one another. I want to be able to get the mean and median across the dataframes.</p>
  
  <pre><code>         Source.0  Source.1  Source.2  Source.3
  cluster                                        
  0        0.001182  0.184535  0.814230  0.000054
  1        0.000001  0.160490  0.839508  0.000001
  2        0.000001  0.173829  0.826114  0.000055
  3        0.000432  0.180065  0.819502  0.000001
  4        0.000152  0.157041  0.842694  0.000113
  5        0.000183  0.174142  0.825674  0.000001
  6        0.000001  0.151556  0.848405  0.000038
  7        0.000771  0.177583  0.821645  0.000001
  8        0.000001  0.202059  0.797939  0.000001
  9        0.000025  0.189537  0.810410  0.000028
  10       0.006142  0.003041  0.493912  0.496905
  11       0.003739  0.002367  0.514216  0.479678
  12       0.002334  0.001517  0.529041  0.467108
  13       0.003458  0.000001  0.532265  0.464276
  14       0.000405  0.005655  0.527576  0.466364
  15       0.002557  0.003233  0.507954  0.486256
  16       0.004161  0.000001  0.491271  0.504568
  17       0.001364  0.001330  0.528311  0.468996
  18       0.002886  0.000001  0.506392  0.490721
  19       0.001823  0.002498  0.509620  0.486059
  
           Source.0  Source.1  Source.2  Source.3
  cluster                                        
  0        0.000001  0.197108  0.802495  0.000396
  1        0.000001  0.157860  0.842076  0.000063
  2        0.094956  0.203057  0.701662  0.000325
  3        0.000001  0.181948  0.817841  0.000210
  4        0.000003  0.169680  0.830316  0.000001
  5        0.000362  0.177194  0.822443  0.000001
  6        0.000001  0.146807  0.852924  0.000268
  7        0.001087  0.178994  0.819564  0.000354
  8        0.000001  0.202182  0.797333  0.000485
  9        0.000348  0.181399  0.818252  0.000001
  10       0.003050  0.000247  0.506777  0.489926
  11       0.004420  0.000001  0.513927  0.481652
  12       0.006488  0.001396  0.527197  0.464919
  13       0.001510  0.000001  0.525987  0.472502
  14       0.000001  0.000001  0.520737  0.479261
  15       0.000001  0.001765  0.515658  0.482575
  16       0.000001  0.000001  0.492550  0.507448
  17       0.002855  0.000199  0.526535  0.470411
  18       0.000001  0.001952  0.498303  0.499744
  19       0.001232  0.000001  0.506612  0.492155
  </code></pre>
  
  <p>Then I want to get the mean of these two dataframes.</p>
  
  <p>What is the easiest way to do this?</p>
  
  <p>Just to clarify I want to get the mean for each particular cell when the indexes and columns of all the dataframes are exactly the same.</p>
  
  <p>So in the example I gave, the average for <code>[0,Source.0]</code> would be (0.001182 + 0.000001) / 2 = 0.0005915.</p>