title: How to merge several csv columns into one column using python 2.7?
body: <p>I'm working with large set of csv data and I want to put several columns in different places into one column separated by semi-colon(;).</p>
  
  <p>So what I have now is..</p>
  
  <pre><code>a   b   c   d
  1   2   3   4
  1   2   3   4
  1   2   3   4
  </code></pre>
  
  <p>I want to change this like..this, So all my data is only in column d.</p>
  
  <pre><code>a   b   c   d
              a=1;b=2;c=3;d=4;
              a=1;b=2;c=3;d=4;
              a=1;b=2;c=3;d=4;
  </code></pre>
  
  <p>I know how to delete those empty column a,b and c but I just can't figure out a way to merge the data from column a,b,c into column d.
  Thanks in advance.</p>
  
  <p>The code that I have so far is..</p>
  
  <pre><code># Parsing the custom formatted data with csv module.
  # reads the custom format input and spits out the output in VCF format.
  import csv
  # input and output
  with open('1-0002', 'rb') as csvin, open('converted1','wb') as csvout:
      # reading and writing are all tab delimited
      reader = csv.reader(csvin, delimiter = '\t')
      writer = csv.writer(csvout, delimiter = '\t')
      # add headings before the for loop to prevent the heading being affected by column manipulation.
      writer.writerow(["#CHROM","POS","ID","REF","ALT","QUAL","FILTER","INFO"])
  
      for row in reader:
          # deleting unnecessary columns, 'del' operator must be in ascending order or else it will give range error
          # manually deleting columns since the input data is in custom format.
          del row[11]
          del row[10]
          del row[9]
          del row[8]
          del row[7]
          del row[6]
          del row[5]
          del row[1]
          del row[0]
          # inserting 1 and . in specific columns
          row.insert(0,'1')
          row.insert(2,'.')
          row.insert(5,'.')
          row.insert(7,'') # inserting empty column for INFO headings.
  
          # change 'YES' to 'PASS' , leaving HETERO as it is.
          if row[6] == 'YES':
                  row[6] = 'PASS'
  
          writer.writerow(row)
  </code></pre>
  
  <p>So from this code above, I want to put the data from several different columns into INFO column.</p>