title: select certain dates inside loop for .csv file
body: <pre><code>Name,USAF,NCDC,Date,HrMn,I,Type,Dir,Q,I,Spd,Q
  
  OXNARD,723927,93110,19590101,0000,4,SAO,270,1,N,3.1,1, 
  OXNARD,723927,93110,19590101,0100,4,SAO,338,1,N,1.0,1, 
  OXNARD,723927,93110,19590101,0200,4,SAO,068,1,N,1.0,1, 
  OXNARD,723927,93110,19590101,0300,4,SAO,068,1,N,2.1,1, 
  OXNARD,723927,93110,19590101,0400,4,SAO,315,1,N,1.0,1, 
  OXNARD,723927,93110,19590101,0500,4,SAO,999,1,C,0.0,1, 
  ....
  
  OXNARD,723927,93110,19590102,0000,4,SAO,225,1,N,2.1,1,
  OXNARD,723927,93110,19590102,0100,4,SAO,248,1,N,2.1,1,
  OXNARD,723927,93110,19590102,0200,4,SAO,999,1,C,0.0,1,
  OXNARD,723927,93110,19590102,0300,4,SAO,068,1,N,2.1,1,
  </code></pre>
  
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  <p>Here is a snippet of a csv file storing hourly wind speeds (Spd) in each row.  What I'd like to do is select all hourly winds for each day in the csv file and store them into a temporary daily list storing all of that day's hourly values (24 if no missing values).  Then I'll output the current day's list, create new empty list for the next day, locate hourly speeds in the next day, output that daily list, and so forth until the end of the file.</p>
  
  <p>I'm struggling with a good method to do this.  One thought I have is to read in line i, determine the date(YYYY-MM-DD), then read in line i+1 and see if that date matchs date i.  If they match, then we're in the same day.  If they don't, then we are onto the next day. But I can't even figure out how to read in the next line in the file...</p>
  
  <p>Any suggestions to execute this method or a completely new (and better?!) method are most welcome.  Thanks you in advance!</p>
  
  <pre><code>obs_in  = open(csv_file).readlines()
  for i in range(1,len(obs_in)):        
  # Skip over the header lines 
  if not str(obs_in[i]).startswith("Identification") and not str(obs_in[i]).startswith("Name"):
      name,usaf,ncdc,date,hrmn,i,type,dir,q,i2,spd,q2,blank = obs_in[i].split(',')
      current_dt  = datetime.date(int(date[0:4]),int(date[4:6]),int(date[6:8]))
      current_spd = spd 
      # Read in next line's date: is it in the same day?
      # If in the same day, then append spd into tmp daily list 
      # If not, then start a new list for the next day 
  </code></pre>