title: missing values writing a csv file with python
body: <p>I am trying to write a csv file with python from a dictionnary which looks like follows:</p>
  
  <pre><code>1: [(3456,12),(4521,78)]
  2: [(5478,45),(5609,43)]
  3: [(8756,34),(6721,90)]
  </code></pre>
  
  <p>etc ...</p>
  
  <p>I have several dictionaries like this. They can have until 30 keys. To write all the dictionnaries in a csv file, I wrote the following code which will be applied to each dictionnary:</p>
  
  <pre><code>for i,j in dictionnary.iteritems():
     for k in j:
       cr=csv.reader(open('/home/file.csv','rb'))
       datalist=list(cr)
       c=writerows(datalist+[[self.user_id, i,k[0],k[1]])
  </code></pre>
  
  <p>When I open the csv file, only a part of the dictionary is written. When I run multiple times the code, not the same entries of the dictionary are missing.
  I don't understand what happens. Where could the problem come from?  </p>