Learn how to enhance a dropdown menu in a Python-based dashboard by adding a default “All Manufacturers” option and updating the filtering logic accordingly. This article walks through restructuring the dropdown input and refining the backend logic to ensure the correct data displays based on user selection.
Key Insights
- Convert the manufacturer options into a Python list to allow dynamic insertion of an "All Manufacturers" option at the beginning using the insert method.
- Update the filtering logic to handle the "All Manufacturers" case by displaying the full dataset when this option is selected, while still allowing filtering by individual manufacturers.
- Noble Desktop demonstrates how to structure conditional logic to accommodate future enhancements, such as additional filters like engine size, by setting up an initial dataset that can be further refined.
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In order to add this drop-down option for all manufacturers, let's take a look at that. Right now we just have Acura as the default. If I reload, that's the start.
We want it to be the very first thing in this menu, and we want it to be the selected option to begin with. So to do that, we're currently just grabbing this. What we want is for this to be a list.
And if we make it a Python list, then we can add to it. We can't really add to this. So let's listify it.
We'll call the list function on it. And since we are going to add, before I go any further, since we are going to add all manufacturers, that's not really a manufacturer. All manufacturers, that's not a company.
So we're going to change this name from manufacturers to be the more accurate drop-down options. And now down here where we're setting the options on our drop-down, it'll be our drop-down options, like that. All right.
Now before, let me also organize this a little bit. This probably belongs up here. Here we go.
So, yeah, I think that's better organized. Now we want to add to our drop-down options. With Python, we can add to the start of a list using .insert. So I can say drop-down options.insert. And when we insert, as it says here, we can tell it the index to insert, and the second argument is the object, meaning anything.
It says here any. It could be anything we're inserting. We're going to insert at index zero, meaning at the very start, the string all manufacturers, a word that is impossible to spell without thinking really hard about it.
Okay. That's not quite going to work. All manufacturers is none of them.
There's no manufacturers. The rest of it still works. And as you can see, the insertion worked.
We should also, while we're at it, even though it doesn't work yet, make this is our initial value for our drop-down. We should make it the all manufacturers option. There we go.
Which, again, still doesn't work. But now it's in the correct place. We've got the correct user behavior.
We don't have the correct code behavior. Or rather, we have the right interface behavior, the right interface, initial interface, but we don't have it functional yet. So our next step is to, when we update the graph, right now this is not working because no rows meet this criterion, this condition, where the manufacturer column has as a value all manufacturers, the initial value.
So what we're going to do is, that's not too hard to fix. We're going to say right away, we're going to make this, we're going to surround this filtered cars with just an if. If selected manufacturer is not all manufacturers, do this.
You can see there's an error here because right now this isn't actually part of the if. And there's no, there's nothing that is part of the if. So we need to indent this.
Now it's part of the if. Now, if the selected manufacturer is not equal to all manufacturers, we'll filter it. But we need a value for if it is all manufacturers.
If it is all manufacturers, before this, we'll just set filtered cars to equal cars. So if all manufacturers, if it is all manufacturers, well then this won't run, which is correct because that won't work. And instead, filtered cars will just be all the cars.
Let's, let's check this out. Let's see if it works. There they are.
There they all are. We can switch to any of these. These still work.
If I switch back to all manufacturers, that works too. So every time it's updating the graph now, it's saying filtered cars is all the cars, just in case this is not true. But if it is true, as long as not all manufacturers, change that.
Nevermind. Filtered cars is that particular selected manufacturer. You might do this a different way.
You might say filtered cars is filtered cars. You know, we might say if it's all manufacturers, then set it back to cars. There's a number of different ways to do this.
Maybe an if else might be a good choice. The reason I'm doing it this way is we are going to next filter by a different criterion. We're going to filter by engine size in addition.
And we're going to do that whether it's all manufacturers or any. So this line will get a little longer. That's why I did it in this maybe slightly confusing way.
But to clear it up, this is, hey, start out with it being all cars, just in case it's all manufacturers. If it's not all manufacturers, filter it farther by the selected manufacturer. And in fact, one other change I need to make, we're not going to filter all cars that way, because in a minute, we are going to add in a criterion here.
Filter by engine size. So this should not be filtering all cars. It should be doing the cars we've filtered so far.
Filter those. Which again, right now is just all cars anyway. But in a minute, it's going to get a second filter.