title: Automatically freeing memory of no more used variables in python
body: <p>I'm new in Python.
  Let's say, I use large pandas data frames.
  My code looks something like:</p>
  
  <pre><code>all_data = pd.read_csv(huge_file_name)
  part_data = all_data.loc['ColumnName1', 'ColumnName2','ColumnName3']
  data_filtered = part_data.loc[:,part_data['ColumnName2']==-1]
  </code></pre>
  
  <p>and so on.
  Is some way, that python can delete all_data, part_data and other variables no more used?
  I can write <code>del var_name</code>, but it will change the code to be very dirty.
  Also I can use for all variables the same name, but it also doesn't look good.
  Thank you all in advance!</p>