Delete all objects in a list

Question

I create many object then I store in a list  But I want to delete them after some time because I create news one and don t want my memory goes high  in my case  it jumps to 20 gigs of ram if I don t delete it    Here is a little code to illustrate what I trying to do   class test      def   init   self           self a    Hello World      def kill self           del self  a   test   b   test   c    a b   print  1 Before   a b   for i in c      del i  for i in c      i kill       print  2 After   a b    A and B are my objects  C is a list of these two objects  I m trying to delete it definitely with a for-loop in C  one time with DEL and other time with a function  It s not seem to work because the print continue to show the objects   I need this because I create 100 000 objects many times  The first time I create 100k object  the second time another 100k but I don t need to keep the previous 100k  If I don t delete them  the memory usage goes really high  very quickly

User · Answer

If the goal is to delete the objects a and b themselves  which appears to be the case   forming the list  a  b  is not helpful  Instead  one should keep a list of strings used as the names of those objects  These allow one to delete the objects in a loop  by accessing the globals   dictionary   c     a    b     create and work with a and b     for i in c      del globals   i

User · Answer

tl dr  mylist clear      Added in Python 3 3 del mylist     are probably the best ways to do this   The rest of this answer tries to explain why some of your other efforts didn t work   cpython at least works on reference counting to determine when objects will be deleted   Here you have multiple references to the same objects   a refers to the same object that c 0  references   When you loop over c  for i in c    at some point i also refers to that same object   the del keyword removes a single reference  so  for i in c     del i  creates a reference to an object in c and then deletes that reference -- but the object still has other references  one stored in c for example  so it will persist  In the same way  def kill self       del self  only deletes a reference to the object in that method   One way to remove all the references from a list is to use slice assignment  mylist   list range 10000   mylist         print mylist   Apparently you can also delete the slice to remove objects in place  del mylist      This will implicitly call the    delslice    or    delitem    method   This will remove all the references from mylist and also remove the references from anything that refers to mylist   Compared that to simply deleting the list -- e g  mylist   list range 10000   b   mylist del mylist  here we didn t get all the references to the objects we created     print b    0  1  2  3  4        Finally  more recent python revisions have added a clear method which does the same thing that del mylist    does  mylist    1  2  3  mylist clear   print mylist

User · Answer

To delete all objects in a list  you can directly write list       Here is example    gt  gt  gt  a    1  2  3   gt  gt  gt  a  1  2  3   gt  gt  gt  a       gt  gt  gt  a

User · Answer

Here s how you delete every item from a list   del c      Here s how you delete the first two items from a list   del c  2    Here s how you delete a single item from a list  a in your case   assuming c is a list   del c 0

[python] Delete all objects in a list

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