Python Fundamentals

Combining, Comparing, & Contrasting

Python Fundamentals

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The "Combining, Comparing, & Contrasting" Lesson is part of the full, Python Fundamentals course featured in this preview video. Here's what you'd learn in this lesson:

Nina demonstrates how to create a set with elements from two sets, how to find the similarities between sets, and how to find how two sets differ. Frozen sets are also briefly covered.


Transcript from the "Combining, Comparing, & Contrasting" Lesson

>> Nina Zakharenko: We can use operations to compare items between two sets, and there's just a cheat sheet here for some of them. There's more than this, but these are the ones that I generally find useful. So union or pipe symbol creates a new set with all the items from both s and t, and let's see that in action.

>> Nina Zakharenko: And very quickly just like list, if I wanna find out if an item is in my set or not, I can use the In keyword. So if I have a set of colors,
>> Nina Zakharenko: I can say is blue in colors? It is. Is orange in colors? It's not.

There is some other methods on list that help us figure out if items were in there or not. One of those was .index. Do you think set has a .index? No, because the items in the set, they aren't positional. Just think about it like Santa's bag of presents, right?

He's got presents in there, kind of all jumbled up. Doesn't really matter, right?
>> Nina Zakharenko: For a list, we also used a count method, right? Like to find out how many times a particular item appeared in the list. Does sets have a count method? No, right? Because each item is only in there once.

Once it's in there that's it, if I try to add it to the set again it's not gonna get updated. Now set operations are really useful. So I'm gonna make two sets of colors and I recommend that you make your own sets. So the first one is gonna be the rainbow colors, and those are the same for everyone; red, orange, yellow, green, blue, and violet.

And now make a new set of your favorite colors. Based on my hair, my favorite color is obviously pink, right? Pink hair, pink laptop, but I also like color black, I like the color blue.
>> Nina Zakharenko: So now you should have two sets. Just for clarity I'm gonna rename my favorite set favorite colors just so you can kind of follow along with me.

To do that I can just assign a new variable to that one. Looking at my rainbow colors, red, orange, they're all in there. My favorite colors, black, blue, and pink.
>> Nina Zakharenko: Now.
>> Nina Zakharenko: We can use the union operator to create a new set that contains all of the items from both rainbow colors and favorite colors.

>> Nina Zakharenko: Remember you can use my set.union, other set,
>> Nina Zakharenko: Or you can use my_set, and this pipe symbol that means union.
>> Nina Zakharenko: Other set. Okay, so let's try this with rainbow colors and favorite colors.
>> Nina Zakharenko: And so all the items from rainbow colors and all the items from favorite colors.

And we'll see that the set is a little bit shorter, right? All the items combined are shorter than the sets with the two different elements in them. Why is that?
>> Speaker 2: Remove the duplicates.
>> Nina Zakharenko: Right, remove the duplicates
>> Nina Zakharenko: Okay, next is the intersection.
>> Nina Zakharenko: So that's creating a new set with only the items that appear in both sets.

And the symbol for intersection is the ampersand. So, rainbow rainbow_colors & favorite_colors. For me, that's just blue. Depending on what your favorite colors are, you might see more results or you might see less. Or you might get back nothing.
>> Nina Zakharenko: Now, lastly we're also gonna find the difference.

The difference is, it's creating a new set with all the items that are in one, but not in the other side. So to do that we use this hat character. That's the difference.
>> Nina Zakharenko: And we'll see that blue Is missing from this list, right? Blue was in both and now it's gone, that's the intersection.

>> Nina Zakharenko: There are a lot of other useful operations available on set. You can see if one set is a subset of another set, or superset, there's a lot more. I don't have time to cover them all. Python also has a frozen set type available. If you need the functionality of a set, but you might want it to be what?

>> Speaker 3: Immutable.
>> Nina Zakharenko: Gold star, exactly right. Did everyone hear? Yeah, if you want your set to be a immutable, you can use a frozen set.
>> Nina Zakharenko: And don't forget, you can always call help on set, or dim, do a little bot of exploring. So if I wanted to call help on set.union, I would just have to pass in that method, and it'll kinda give me a helpful hint that union returns the union of sets as a new set.

Actually, that's not a good explanation, right? It's like the definition is the definition.
>> Speaker 3: [LAUGH]

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