title: Reading in repeated blocks of data using pandas and python
body: <p>I have a file with the following data:</p>
  
  <pre><code>       2008   1   1     ATMOS CO2 = 382. ppm
                                                     SOIL LAYER NO
                          1           1           2           3           4         TOT
         DEPTH(m)        0.01        0.10        0.33        0.64        0.81
   BD 33kpa(t/m3)        1.48        1.48        1.48        1.50        1.53
          SAND(%)        82.2        82.2        82.2        66.9        67.4
          SILT(%)         5.3         5.3         9.8        23.1        19.6
          CLAY(%)        12.5        12.5         8.0        10.0        13.0   
      WHSC(kg/ha)        525.       4729.       4480.       6119.       1114.      16968.
      WHPC(kg/ha)       1123.      10104.       9572.      13076.       2381.      36256.
       WOC(kg/ha)       1717.      15455.      14638.      19995.       3641.         55.
  
  
  
           2008  12  31     ATMOS CO2 = 382. ppm
                                                     SOIL LAYER NO
                          1           1           2           3           4         TOT
         DEPTH(m)        0.01        0.10        0.33        0.64        0.81
   BD 33kpa(t/m3)        1.48        1.48        1.48        1.50        1.53
          SAND(%)        81.4        81.4        81.4        67.7        67.4
          SILT(%)         6.5         6.5        10.3        22.3        19.6
          CLAY(%)        12.1        12.1         8.2        10.0        13.0
      WHSC(kg/ha)        499.       4559.       4291.       6017.       1117.      16483.
      WHPC(kg/ha)       1123.      10109.       9576.      13081.       2382.      36271.
       WOC(kg/ha)       1633.      14757.      13993.      19316.       3601.         53.
  </code></pre>
  
  <p>Each block begins with the date of the year e.g. <code>2008 1  1</code> denotes 1st January 2008 and <code>2008    12    31</code> denotes 31st Decemeber 2008.</p>
  
  <p>In each block, there are values for several parameters e.g. DEPTH, SAND(%), WOC etc. I want to extract values for WOC for a user given year
  and day and month e.g. 2008  12   31, and  for a specific column e.g. TOT. I can read the dataframe but not sure what is the best way to proceed after that:</p>
  
  <pre><code>df = pandas.read_csv('data.txt')
  </code></pre>