Python Sets

In Python, sets are an unordered collection of unique elements. They are useful for various operations, such as removing duplicates from a list, testing membership, and performing set operations like union, intersection, and difference. Here's a basic lesson on sets in Python:

### Creating Sets:

You can create a set in Python using curly braces `{}` or the `set()` constructor:

```python

# Using curly braces

my_set = {1, 2, 3, 4, 5}

# Using set() constructor

another_set = set([4, 5, 6, 7, 8])

```

### Basic Operations:

#### 1. Adding Elements:

You can add elements to a set using the `add()` method:

```python

my_set.add(6)

```

#### 2. Removing Elements:

Use the `remove()` method to remove an element. If the element is not present, it raises a `KeyError`. Alternatively, you can use `discard()` to remove an element without raising an error if it's not present.

```python

my_set.remove(3)

# or

my_set.discard(3)

```

#### 3. Set Operations:

Python provides several set operations like union (`|`), intersection (`&`), difference (`-`), and symmetric difference (`^`):

```python

set1 = {1, 2, 3, 4, 5}

set2 = {3, 4, 5, 6, 7}

# Union

union_set = set1 | set2

# Intersection

intersection_set = set1 & set2

# Difference

difference_set = set1 - set2

# Symmetric Difference

symmetric_difference_set = set1 ^ set2

```

### Set Methods:

#### 1. `union()`, `intersection()`, `difference()`, `symmetric_difference()`:

These methods provide alternatives to the set operators mentioned above:

```python

union_set = set1.union(set2)

intersection_set = set1.intersection(set2)

difference_set = set1.difference(set2)

symmetric_difference_set = set1.symmetric_difference(set2)

```

#### 2. `issubset()` and `issuperset()`:

Check if one set is a subset or superset of another:

```python

is_subset = set1.issubset(set2)

is_superset = set1.issuperset(set2)

```

### Membership Test:

You can check if an element is present in a set using the `in` keyword:

```python

if 3 in my_set:

print("3 is in the set.")

```

### Frozen Sets:

A `frozenset` is an immutable version of a set. Once created, you cannot add or remove elements from it:

```python

frozen_set = frozenset([1, 2, 3, 4])

```

Sets in Python are versatile and can be handy in various situations where you need to work with unique elements or perform set operations efficiently.