title: Python csv module throws "Error: sequence expected" at writer.writerow
body: <p>I use psycopg2 to connect postgresql and python, and here's my script,</p>
  
  <pre><code>import sys
  
  #set up psycopg2 environment
  import psycopg2
  
  #driving_distance module
  query = """
      select *
      from driving_distance ($$
          select
              gid as id,
              start_id::int4 as source,
              end_id::int4 as target,
              shape_leng::double precision as cost
          from network
          $$, %s, %s, %s, %s
      )
  """
  
  #make connection between python and postgresql
  conn = psycopg2.connect("dbname = 'TC_routing' user = 'postgres' host = 'localhost' password = '****'")
  cur = conn.cursor()
  
  #count rows in the table
  cur.execute("select count(*) from network")
  result = cur.fetchone()
  k = result[0] + 1
  
  #run loops
  rs = []
  i = 1
  while i &lt;= k:
      cur.execute(query, (i, 1000000, False, False))
      rs.append(cur.fetchall())
      i = i + 1
  
  h = 0
  ars = []
  element = list(rs)
  while h &lt;= 15:
      rp = element[0][h][2]
      ars.append(rp)
      h = h + 1
  
  print ars
  conn.close()
  </code></pre>
  
  <p>the output is fine,</p>
  
  <pre><code>[0.0, 11810.7956476379, 16018.6818979217, 18192.3576530232, 21507.7366792666, 25819.1955059578, 26331.2523709618, 49447.0908955008, 28807.7871013087, 39670.8579371438, 42723.0239515299, 38719.7320396044, 38265.4435766971, 40744.8813155033, 43770.2158657742, 46224.8748774639]
  </code></pre>
  
  <p>but if I add some lines below in order to export results to the csv file, I got this error,</p>
  
  <pre><code>import csv
  
  with open('test.csv', 'wb') as f:
      writer = csv.writer(f, delimiter = ',')
      for row in ars:
          writer.writerow(row)
  </code></pre>
  
  <hr>
  
  <pre><code>[0.0, 11810.7956476379, 16018.6818979217, 18192.3576530232, 21507.7366792666, 25819.1955059578, 
  26331.2523709618, 49447.0908955008, 28807.7871013087, 39670.8579371438, 42723.0239515299, 38719.7320396044, 38265.4435766971, 40744.8813155033, 43770.2158657742, 46224.8748774639]
  
  Traceback (most recent call last):
    File "C:/Users/Heinz/Desktop/python_test/distMatrix_test.py", line 54, in &lt;module&gt;
      writer.writerow(row)
  Error: sequence expected
  </code></pre>
  
  <p>How to fix this？</p>
  
  <p>I am working with python 2.7.6 and pyscripter under Windows 8.1 x64. Feel free to give me any suggestion, thanks a lot!</p>