Section 9.7 Deleting elements
There are several ways to delete elements from a list. If you know the index of the element you want, you can use pop:
pop modifies the list and returns the element that was removed. If you don't provide an index, it deletes and returns the last element.
Checkpoint 9.7.1.
alist = [4, 2, 8, 6, 5]
temp = alist.pop(2)
temp = alist.pop()
print(alist)
[4, 8, 6]
pop(2) removes the item at index 2, not the 2 itself.
[2, 6, 5]
pop() removes the last item, not the first.
[4, 2, 6]
Yes, first the 8 was removed, then the last item, which was 5.
Checkpoint 9.7.2.
alist = [4, 2, 8, 6, 5]
alist = alist.pop(0)
print(alist)
[2, 8, 6, 5]
alist is now the value that was returned from pop(0).
[4, 2, 8, 6, 5]
pop(0) changes the list by removing the first item.
4
Yes, first the 4 was removed from the list, then returned and assigned to alist. The list is lost.
None
pop(0) returns the first item in the list so alist has now been changed.
If you don't need the removed value, you can use the del operator:
If you know the element you want to remove (but not the index), you can use remove:
The return value from remove is None.
To remove more than one element, you can use del with a slice index:
As usual, the slice selects all the elements up to, but not including, the second index.
Checkpoint 9.7.3.
alist = ['a', 'b', 'c', 'd', 'e', 'f']
del alist[1:5]
print(alist)
['a', 'b', 'c', 'd', 'e', 'f']
The del method removes part of the list, so it will be shorter.
['a', 'f']
'a' is the 0th element of the list and 'f' is the 5th element of the list, so these are the values that remain after deleting [1:5].
['f']
Remember that lists start at 0, not 1, and that a slice stops before the second element - not after.
['b', 'c', 'd', 'e']
These are the values that will be deleted with the slice [1:5]
Checkpoint 9.7.4.
