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- [Instructor] In this video,

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we're going to introduce another way

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to delete elements from a list,

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using the del, or delete, statement,

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which is not only capable
of deleting from a list,

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but also capable of deleting variables

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from an Interactive
Python session as well.

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So we'll demonstrate those cases to you.

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Now, for the purpose of this example,

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we'll once again work
with a list of numbers.

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For this one, let's say we
want to produce the range

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of values zero through nine.

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And, of course, if we go
ahead and evaluate numbers,

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we can see the contents of that list.

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Now, the del statement
can be used to remove,

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from a list, any valid index position

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or any subset slice that you specify.

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So, for example, if I go ahead and say

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del numbers sub minus one,

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that says delete the
last element of the list.

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And if I now go and reevaluate numbers,

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we can see there's one
fewer element in the list.

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The nine has been removed.

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Now, like I said, you
can also delete slices.

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So if I say delete numbers

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sub zero colon two,

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and again, zero in this case is implicit

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because it's the start of the list,

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so I could just say del numbers colon two

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in the square brackets,

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and in this case,

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we can go ahead and take a look at numbers

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and see that the first two elements,

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the slice from zero,

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up to but not including
index position two,

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has been removed from the
beginning of the list.

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Now, as you might expect,

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you don't have to delete
consecutive elements

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in a slice because any
valid slice can be used.

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So if I now go ahead and say

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let's delete from numbers
every other remaining element,

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that's going to start from index zero,

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which will be inferred as the first index,

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go all the way through the list,

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so the length of the list will be inferred

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as the second index,

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and every other element will be removed.

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So we'll delete the two,
four, six, and eight

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from the remaining list,

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and if we now go ahead
and evaluate numbers,

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we see that only three, five,
and seven are remaining.

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And, as you would also probably expect now

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based on what we've shown you with slices,

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we could even do delete numbers colon,

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in square brackets, which just
says delete all the elements

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of the list numbers,

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and now it is an empty list.

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So, as I mentioned towards
the beginning of this video,

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in addition to being able to
delete elements from a list,

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which is a mutable object,

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so you can't do this for
slices or strings for example,

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but in addition to modifying lists,

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you can also delete variables

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from the current session as well.

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So if I simply say delete numbers,

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that literally says remove
the variable numbers

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from this interactive IPython session.

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So now if I try to evaluate numbers,

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it tells me that that name is not defined

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here in the current session.