#100DaysOfCode in Python Transcripts
Chapter: Days 7-9: Python Data Structures
Lecture: Creating and Parsing Dictionaries
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Alright.
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Next up we're going to talk about dictionaries,
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or dicts for short,
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let's keep saying dictionaries, just to be safe.
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And they're made up of pretty much two different things.
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The easiest way to demonstrate it is to just create one
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in its simplest form.
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So we'll create a dictionary called pybites,
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and let's just add a few things to it.
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The first thing we need to add is a key,
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and the second thing we need to add is a value.
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Alright.
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Looking at it here, there's a separator here, your colon.
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And that separates your key, the key comes first,
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from your value on the end.
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Alright, and this here is technically a dictionary.
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It may only have one item in it, but it's a dictionary
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all the same.
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Let's make it a little more interesting.
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When you're adding a second item into your dictionary,
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you separate it with a comma.
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Alright, so we've got Julian, now let's add Bob,
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and let's just say he's 33, then we have Mike,
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let's say he's also 33.
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Let's just say I'm being super generous with those ages
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guys, anyway, there's our dictionary.
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So to view what it looks like, we just type in,
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pybites.
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And there it is there, the three different items.
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And these link to each other.
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So the key is Mike, the value is 33.
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The key is Bob, the value is also 33.
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Now notice when we printed it out, it printed out
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in this order.
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Well this order is not explicit.
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With a dictionary, when you're passing it,
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when you're listing it out, when you're displaying it,
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there's no guarantee that the data is going to remain
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in the order, okay?
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That's very important to remember with dictionaries,
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they are unordered, okay?
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Now let's say we wanted to create a dictionary
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but we didn't know what values we were going to put into it
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from the start.
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We'll just do a quick little side track demonstration here.
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You would start off just as you would do with a list
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that's empty, except you're using two curly brackets
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instead of the square ones.
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So people is now an empty dictionary.
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There's absolutely nothing in it.
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To add someone to it, this is the tricky part, this is where
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it gets a bit different.
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What you need to do, you need to actually pretty much
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in square brackets, you need to choose the key, alright?
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In this instance the key for a list of people is going
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to be Julian, and we're going to assign that key a value
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of 30.
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So the dictionary people, we're creating an entry,
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a key, of Julian, and we're assigning it the value of 30.
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We list out people, there we go, we see that exact same
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formatted dictionary as we did when we explicitly
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defined it up here, okay?
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We can add to it again.
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We can go, people, Bob, and we can assign Bob
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the age this time of 103.
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And there we go.
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So same thing, right?
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This time we just populated an empty dictionary.
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But either way it all comes out the same.
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Now the way you interact with the dictionaries is a bit
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different to lists.
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The way we view just the keys, just these keys here,
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forget the values for a minute,
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is we use keys.
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So we can go pybites.keys, and there are our
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dictionary keys.
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Julian, Bob, Mike.
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The same things for the values.
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pybites.values, and there we go, the three values.
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30, 33, and 33.
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Now what if we wanted to see all of this?
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Now this is all well and good because we're in the shell.
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But if this was an actual application you can't just
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type in the name of your dictionary and expect it
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to print out, right?
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This is just all standard out through the shell.
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So the way we would actually print out, first of all,
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the way we actually see each pair of dictionary items
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is to use items().
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We can see Julian 30, Bob 33, Mike 33.
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These are our three different dictionary key value
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combinations or items.
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Now how do we pass over all of that?
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Well we do it just how we would with a normal list.
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We can go for keys in pybites.keys, print keys.
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There we go.
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We can do for values in PieBites.values, print values.
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Okay?
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This is all very similar, you can see the similarities
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between dictionaries and lists.
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But last but not least, what if we want to print out
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all of this information, not just keys, not just values,
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without having to run two separate for loops, which would
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be quite un-pythonic right?
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Well, God love Python, we can go for keys values in
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pybites.items(), so for keys and values in PieBites.items
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Print keys, and remember we have to do the string thing
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here, values, and there we go.
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Julian 30, Bob 33, Mike 33.
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Now obviously that is not very pleasant on the eye,
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so we can do our standard string formatting.
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So we can go, for keys, values in pybites.items(),
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print, string is digit years of age, keys, values, okay?
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And there we go. We can see Julian is 30 years of age,
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Bob is 33 years of age, Mike is 33 years of age.
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And that's dictionaries.
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It's actually that simple to iterate over dictionary,
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and that's pretty much it.
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You've got your key, and your value.
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And you just do it over and over again,
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just like a list.
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So enjoy your dictionaries, and get used to them,
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because you'll be playing with them.
