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Python Sets

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Set Mutability: Adding Elements

4:44 with AJ Tran

Sets are mutable containers. If an element is not already in a set, it can be added to the set at any time.

Adding Elements into a Set

Use .add() to add single items to a set.

Use .update() to add many items from an iterable into a set.

These two methods will have no effect if an element is already a member of the set

secondary_colors = set()

secondary_colors.add('orange')
secondary_colors.add('purple')
secondary_colors.add('green')
secondary_colors.add('green')
secondary_colors.add('green')

print(secondary_colors)
# {'green', 'orange', 'purple'}


fancy_colors = set()

fancy_colors.update(['aquamarine', 'emerald green', 'tiffany blue'])
fancy_colors.update(['tiffany blue', 'bacon red'])

print(fancy_colors) 
# {'tiffany blue', 'aquamarine', 'bacon red', 'emerald green'}

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    Now that we know different ways to make sets, 0:00
    let's learn about how to manipulate them. 0:04
    We'll start with adding and removing elements. 0:07
    Remember that sets are mutable, that means, 0:11
    that the data inside of a set can be changed after the set is created. 0:15
    There are two methods for adding elements to a set. 0:21
    If an element is already a member, there is no effect. 0:26
    We can add one element at a time with the add method, and 0:29
    we can add many elements all at once with the update method. 0:34
    Let's demonstrate! First, I'll declare a new variable, 0:40
    let's have vowels and assign it as an empty set. 0:46
    Then, we can use the add method to add one element, 0:53
    And I'll add in, A, which was the first vowel, we'll do a capital A. 1:00
    So if I print my vowels out, and 1:09
    I run my script in the console 1:14
    I'll see that I have a set. 1:23
    It's a singleton set with one member and the member is a capital A. 1:25
    This method has no effect if an element is already a member of the set. 1:32
    We'll make a simple check for membership using the "in" keyword. 1:38
    And what I'll do here is I will print out... 1:48
    We see it's true that A is a member of this set of vowels. 2:08
    Now what will happen if I duplicate and 2:16
    add in this A many, many times. 2:21
    When I run my script again, we'll see that I still have a singleton 2:31
    set! Because A is already a member of vowels, it will not be added again. 2:37
    Now, instead of adding in the rest of the vowels one by one, 2:46
    let's add them all together. 2:50
    I can use the update method to add multiple values. 2:53
    It takes an iterable as an argument, just like the set constructor function. 2:58
    I'll use my favorite iterable type, which is a string 3:09
    E, I, O, and U. Just like the set constructor function, 3:16
    the update function will go through every element of the iterable, 3:21
    and then add it into the set. 3:27
    Let's print out my new vowel set after it has been updated. 3:29
    We'll see all of the vowels have been added into the set. 3:40
    When elements are already a member of the set, the method will have no effect. 3:49
    We can see that even though I've tried to add the letter A many times, 3:59
    and then the letters E, I, O and U many times, 4:06
    they're only added into the set just once. 4:11
    So, there's our set of vowels. 4:16
    Notice how the order is non-deterministic for these string data types. 4:20
    So if your vowels come out in a different order, 4:26
    that's totally okay, it's working as intended. 4:30
    Add and update are the two methods for adding elements into a set. 4:34
    Next we'll learn about removing elements from a set. 4:40

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