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Let's talk about changing values in a dictionary.
Alright, so I've decided to upgrade my Virago 

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to the larger model. So let's see how to change a
value in our dictionary. Now you may have worked

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that out already - you just assign the new value to
the same key. Let's go ahead and do that, so I'm

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going to put some code down here on line 16. Put
a comment first, we're going to upgrade the Virago.

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and the actual code will be vehicles
left square bracket double quotes,

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virago, in lower case this time,
to match the key we've already got.

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equals, and we'll put in the value.
In this case, it's going to be Yamaha XV535

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closing double quote. Alright, so let's run the program.

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You can see that our Virago is now the larger,
shaft-drive version - the 535. It's not at the end

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of the output, though. You should find it on line
five, and you can see that in the output pane in my output,

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unless you're using Python 3.5 or earlier,of course,
in which case, it'll be in the output somewhere.

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Notice that the old model - the one we had
previously - is no longer present. Each key in a

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dictionary is unique, which makes sense. If the same
key could appear more than once, how would you know

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which value you were referring to. When you use the
same key again, the new value replaces the old one.

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That should answer a question you may have been
asking. What happens if you use the same key twice,

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in the literal definition of our dictionary.
So let's try that to see. We're going to come up here.

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What I'm going to do is add a new
entry on line 10: single quote roadster

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closing single quote colon,
then another single quote,

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and we're going to add the
value, which is Triumph

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Street Triple, single quote again to
close that off, and a comma. Now, if we run the

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program again now, you can see that we've
only got one roadster in the output. 

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Once again, if you're running Python 3.5 or earlier,
the output will be in a random order.

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I'm using Python 3.8, and that preserves the
insertion order of dictionary keys, and in fact,

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Python 3.7 does the same. Note that it preserves
the insertion order - emphasis on insertion.

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If you expected the roadster to appear after
the fiesta, that should now explain why it doesn't. 

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Our roadster was inserted as the second
entry in the dictionary - that's on line three.

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We then replaced the value with the Street
Triple, on line 10. The keys don't get re-ordered

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when you do that. The insertion order of the keys is preserved.
Notice that the virago is still at position 5 in our output.

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Although we made a change to the value on line 18,

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that doesn't cause the key to be moved.
Also note that if I go back to

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our dictionary, we defined at the top, there's a
warning there from IntelliJ on lines 3 and 10:

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Dictionary contains duplicate keys 'roadster'.
You wouldn't normally use the same key twice 

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in a dictionary literal. It's just a waste of time and
typing. The last value will replace any earlier ones.

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So what I'm going to do is come up here to
line three. Click on that and use the light bulb

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to delete that entry, or remove this key.
You can see that's now disappeared. 

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Alright, so we'll see plenty of examples of adding
and changing keys. In the next video, I want to

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show you a couple of ways to delete an entry
from a dictionary. See you in the next video.