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to only get passengers that match a particular query,
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there's also a way in Django to say passenger.objects.exclude to say
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exclude passengers that satisfy a particular query.
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So I want to exclude passengers who, among their flights,
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have this as one of their flights.
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And so what does this actually mean?
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Well, it means that when I render flight.html,
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there's a couple pieces of information that it should have.
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It needs to know what flight is being rendered.
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It needs to know who is on the flight, who are the passengers.
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But if I want a dropdown where I can choose from all the people
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who aren't already on the flight, like I would
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like to register you for the flight, well, I also
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need all of the non-passengers.
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Passengers except, excluding the ones who are already on the flight,
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and get me all of them is what that .all is ultimately saying.
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And so using that, I now have access to this variable
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called non-passengers that I can use as I'm constructing this page.
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So back on flight.html, I can say, for every passenger in non-passengers,
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let me create a option that I can choose from.
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And the options value is going to be the passenger's ID.
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Because ultimately, when I submit the form, what I care about getting
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is what is the ID of this passenger that I've chosen from this dropdown.
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But of course, the user who's looking at this page,
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they don't want to see people's IDs.
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They want to see people's names.
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So inside of the option tag, we'll go ahead
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and just print out the passenger's name.
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And we'll see in a moment what all of this
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actually looks like in terms of HTML.
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So now that I've created this form, I'll also
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need at the bottom to add an input whose type is submit
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to let myself submit this form to.
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Let's now try running this application.
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It looks like there's a slight error where
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I said view.book instead of views.book.
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Views is the name of the module, since it's in a file called views.py.
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And now, it looks like my server is running OK.
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I can go back to /flights.
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Let me get one of the flights, like New York to London, flight number one.
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And all right.
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Name error.
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Name passenger is not defined.
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This is how Django renders to me errors that are occurring in my Python code.
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Looks like it just means inside of veiws.py I'm referencing passenger,
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but I never imported it.
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So up at the top, I'll go ahead and import passenger as well.
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Now, it seems that my web application is working OK.
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So now, hopefully, I refresh this page, I see flight information.
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I see passengers.
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And I also down at the bottom now see an add passenger section
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with a dropdown list.
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Where I can click on it and see, all right, here
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are the three people that are not already on this flight.
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And so if I want to add Ginny Weasley to this flight,
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I can click Ginny Weasley, click submit, and that submits the form.
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And I'm redirected back to the same flight page.
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Now, Harry and Ginny are both on the flight.
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And in the add passenger list, I see Ron and Hermione as the options for me
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there.
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And so using Django's models, I've been able to very quickly build up
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a reasonably sophisticated application.
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An application that has models, that displays that information to me,
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and lets me manipulate that data.
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And that data is ultimately stored inside of a SQL database.
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And one of the big powers of Django that it really gives to me
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is this admin interface that I ordinarily
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might have had to spend a lot of time designing a web interface that just
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lets me do things like take some person and go ahead and update
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what is their name, what flights are they on,
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and the ability to very quickly add and delete and edit the models
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is something that in a web application could take quite a lot of time
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to be able to build from scratch.
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But Django, very fortunately, gives all of that right to me.
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And this admin interface, even though it is designed by Django,
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it's very customizable in terms of things
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that I can do on this admin interface if I want to manipulate it in certain ways
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in order to add additional features to it as well.
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So we'll see a couple of brief examples of this.
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If I go into admin.py, here's my configuration
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for Django's admin interface.
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And I can say, I would like to configure the admin
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interface in a particular way.
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That in a flight, for example, by default all I saw
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was the flight's origin and destination.
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If I want to be able to see more information about a flight,
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I can say, go ahead and give me a class called flight admin, which is
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going to be a subclass of model admin.
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Where I can specify any particular settings
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that I want to apply to how the flight admin page is displayed.
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So I can-- and all of this is documented on Django's website.
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And you just have to read it to be able to know what configuration options are
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available to you.
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But I can say, in the list display, when you list all the flights
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and display them all to me, what field should I have access to?
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Well, go ahead and show me something like the origin
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and the destination and the duration and maybe also show me the ID, for example.
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So I want to see all of this information when you load a flight.
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And when I register the flight, I'll say register this flight,
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but use the flight admin settings when you do so.
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