title: python list not deallocating memory after clearing the element of the list
body: <p>I am using lot of list in my long running python script written in python 2.7.
  I am using <strong>pympler to identify leaked memory and I found that the list object memory is being increasing</strong>.But I have cleared all list in each iteration.
  The RES memory is being increasing largely.After 3 minutes of execution time, the script takes <strong>130 MB of RES memory</strong>,I have cleared all list and deleted all objects that were referenced in each iteration.
  I clear list using:</p>
  
  <pre><code>   del list1[:]
  </code></pre>
  
  <p>I delete objects that were referenced by using:</p>
  
  <pre><code>   obj=demo_class()
     some code
     del obj
  </code></pre>
  
  <p>Pls help me in reducing the RES memory?</p>
  
  <p>Thank you PyNico,I had tried it by removing the references to the object and using gc.collect() manually,but it had no effect.</p>
  
  <p>I am using 4 dictionaries in my script.when <strong>i ran my script using pympler to find memory leakage</strong>,I found that the <strong>size of list object is increasing incredibly.And these list contains the keys of these dictionary</strong>.<strong>Is these list in build implementation of python dictionary?.</strong></p>