title: Python dataframe: Finding a value in same row as a defined value in a different column
body: <p>I have a large Pandas dataframe:</p>
  
  <pre><code>    Time      P     T   R   H  
  00000.0 1004.6  12.2  96    12  
  00001.0 1004.2  12.1  96    15  
  00002.0 1003.5  11.9  96    21  
  00003.0 1002.8  12.0  96    27  
  00004.0 1002.0  12.1  96    34  
  00005.0 1001.4  12.1  96    39  
  00006.0 1000.3  12.2  96    48
  
  00007.0  999.5  12.1  96    55  
  00008.0  998.9  12.2  96    59  
  00009.0  998.0  12.1  96    67  
  00010.0  997.3  13.1  96    73  
  00011.0  996.9  13.2  97    76 
  
  00013.0  995.3  13.3  97    90  
  00014.0  994.6  13.6  97    96  
  00015.0  994.3  13.5  97    98  
  00016.0  993.6  13.5  96   104  
  00017.0  992.5  13.3  96   114  
  00018.0  991.8  13.3  96   119  
  00019.0  991.7  13.7  97   120  
  </code></pre>
  
  <p>I want to find the value in a row when a value in another column (same row) has a defined value. For example, I want to write a code that find what the "T" value is in same row where the "P" value is 1002.8. </p>