Delete all objects in a list

tl;dr;

mylist.clear()  # Added in Python 3.3del 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 = mylistdel 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)

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]

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]