Published Dec 20 2020

Sets are another important Python data structure.

We can say they work like tuples, but they are not ordered, and they are **mutable**.
Or we can say they work like dictionaries, but they donβt have keys.

They also have an immutable version, called `frozenset`

.

You can create a set using this syntax:

`names = {"Roger", "Syd"}`

Sets work well when you think about them as mathematical sets.

You can intersect two sets:

```
set1 = {"Roger", "Syd"}
set2 = {"Roger"}
intersect = set1 & set2 #{'Roger'}
```

You can create a union of two sets:

```
set1 = {"Roger", "Syd"}
set2 = {"Luna"}
union = set1 | set2
#{'Syd', 'Luna', 'Roger'}
```

You can get the difference between two sets:

```
set1 = {"Roger", "Syd"}
set2 = {"Roger"}
difference = set1 - set2 #{'Syd'}
```

You can check if a set is a superset of another (and of course if a set is a subset of another)

```
set1 = {"Roger", "Syd"}
set2 = {"Roger"}
isSuperset = set1 > set2 # True
```

You can count the items in a set with the `len()`

global function:

```
names = {"Roger", "Syd"}
len(names) # 2
```

You can get a list from the items in a set by passing the set to the `list()`

constructor:

```
names = {"Roger", "Syd"}
list(names) #['Syd', 'Roger']
```

You can check if an item is contained into a set with the `in`

operator:

`print("Roger" in names) # True`

I wrote an entire book on this topic π

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