title: loop through rows of one csv file to find corresponding data in another
body: <p>I got an interesting problem:</p>
  
  <p>file1.csv has a few hundred rows like:</p>
  
  <pre><code>Code,DTime
  1,2010-12-26 17:01
  2,2010-12-26 17:07
  2,2010-12-26 17:15
  </code></pre>
  
  <p>file2.csv has about 11 million rows like:</p>
  
  <pre><code>id,D,Sym,DateTime,Bid,Ask
  1375022797,D,USD,2010-12-26 17:00:15,1.311400,1.311700
  1375022965,D,USD,2010-12-26 17:00:56,1.311200,1.311500
  1375022984,D,USD,2010-12-26 17:00:56,1.311300,1.311600
  1375023013,D,USD,2010-12-26 17:01:01,1.311200,1.311500
  1375023039,D,USD,2010-12-26 17:01:02,1.311100,1.311400
  1375023055,D,USD,2010-12-26 17:01:03,1.311200,1.311500
  1375023063,D,USD,2010-12-26 17:01:03,1.311300,1.311600
  </code></pre>
  
  <p>What i'm trying to do is to write a script that takes each DTime value in file1.csv and finds the first instance of a partial match in the DateTime column of file2.csv, and outputs DateTime, Bid, Ask for that row. The partial match is on the first 16 characters. </p>
  
  <p>Both files are sorted from oldest to newest, so if "2010-12-26 17:01" from file1.csv matched 4 entries in file2.csv, I only need to extract the first one: "2010-12-26 17:01:01"</p>
  
  <p>Not sure how to proceed..  I tried a dictionary but the order of values is important so i'm not sure if that would work. Maybe bring file1's DTime column into a list and for each entry in that list search DateTime in file2? </p>
  
  <p>Thanks guys</p>