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__iter__
6:10In this step, learn how to tackle iterations using your created objects.
In this video,
we're going to tackle dunder iter.
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This dunder method helps Python know how
to handle iterating through an instance,
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like you would with while or for loops.
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Right now, if we tried to
iterate through our instance,
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we would get something like this.
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Car object is not iterable.
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Right now, Python has no clue what you
want it to do here, so let's help it out.
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Now, it doesn't make a lot of sense
to add this method to our car class.
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What would make more sense is
a group of cars at a car dealership.
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Let's create a new class
called dealership.
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Create our init method.
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And give it a list of cars.
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Now we have something to iterate through.
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Let's add our dunder iter method.
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Inside of our method we'll
add yield from self.cars.
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Yield from is a keyword that tells Python
to grab each item in the iterable
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we're giving it here the cars list and
return it.
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Let's see it in action.
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First, create an instance and then loop
through our cars with the for loop.
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Run it, and the console shows our cars.
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Now, how can we combine our two classes?
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We've got one for cars,
and one for a dealership.
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Seems like a match to me.
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Let's remove our cars in the list here.
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So we're back at an empty list.
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Then we can add a method that lets
us add cars to our dealership.
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We'll call this method add_cars.
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It'll take self and a car for arguments.
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And inside the method we'll
append the car to our list.
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Perfect!
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Now we can use this method to
add some cars to our dealership.
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Let's create a few car instances and
add them
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Copy and
paste to make it a little bit faster.
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Now when we run the file,
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we see our new cars in the console.
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Now, if you didn't notice we've got
two dunder methods working together.
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If we comment out the dunder
string method on our car class,
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And run the file, you can
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see we're back at having these
object messages in the console.
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This is because Python is
going into our dealership,
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And grabbing our list of cars.
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Then when each car instance is printed
out, it activates my trap cards.
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No, but it does activate the dunder
string method of our car class
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Nice work, take a few minutes
to try this out on your own.
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You can create two classes like a book and
bookcase, or
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candy and
candy store to practice dunder iter.
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Check the teachers notes
to see what I came up with.
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Keep up the hard work.
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