title: Deleting variable does not erase its memory from RAM memory
body: <p>I am using Python (Canopy) extensively for Earth science application. Because my application is memory consuming, I am trying find way to erase variable that I don't need any more in my programs, I tried to use del command to erase the variable memory, but I found that space used by Canopy is still the same. Any ideas about how to erase variable completely from the memory. 
  thanks</p>