title: Python : AttributeError: 'NoneType' object has no attribute 'append'
body: <p>My program looks like </p>
  
  <pre><code># global
  item_to_bucket_list_map = {}
  
  def fill_item_bucket_map(items, buckets):
      global item_to_bucket_list_map
  
      for i in range(1, items + 1):
          j = 1
          while i * j &lt;= buckets:
              if j == 1:
                  item_to_bucket_list_map[i] = [j]
              else:
                  item_to_bucket_list_map[i] = (item_to_bucket_list_map.get(i)).append(j)
              j += 1
          print "Item=%s, bucket=%s" % (i, item_to_bucket_list_map.get(i))
  
  
  if __name__ == "__main__":
      buckets = 100
      items = 100
      fill_item_bucket_map(items, buckets)
  </code></pre>
  
  <p>When I run this, it throws me</p>
  
  <p><code>AttributeError: 'NoneType' object has no attribute 'append'</code></p>
  
  <p>Not sure why this would happen? When I am already creating a list at start of each <code>j</code></p>