> ## Documentation Index
> Fetch the complete documentation index at: https://python4ai.codewithsiva.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Sets

> Work with unique collections

## What are sets?

Sets are collections that only store unique values. They automatically remove duplicates.

Think of sets like:

* A bag of unique marbles
* Guest list (each person once)
* Unique tags or categories

## Creating sets

You can create sets two ways: with `set()` or with curly braces `{}` (but only when it has values).

```python theme={null}
# Empty set (careful!)
empty_set = set()  # NOT {} - that's a dict!

# Set with values - both ways work
numbers = {1, 2, 3, 4, 5}
fruits = set(["apple", "banana", "orange"])

# From a list (removes duplicates)
scores = [85, 90, 85, 92, 90]
unique_scores = set(scores)  # {85, 90, 92}
```

<Warning>
  Use `set()` for empty sets, not `{}`. Empty curly braces create a dictionary!
</Warning>

## Basic operations

```python theme={null}
colors = {"red", "blue"}

# Add items
colors.add("green")
print(colors)  # {'red', 'blue', 'green'}

# Remove items
colors.remove("blue")    # Error if not found
colors.discard("yellow") # No error if not found

# Check membership
if "red" in colors:
    print("Red is available")
```

## Common uses

### Remove duplicates

```python theme={null}
names = ["Alice", "Bob", "Alice", "Charlie", "Bob"]
unique_names = list(set(names))
print(unique_names)  # ['Alice', 'Bob', 'Charlie']
```

### Fast membership testing

```python theme={null}
allowed_users = {"alice", "bob", "charlie"}

if "alice" in allowed_users:  # Very fast!
    print("Access granted")
```

## Common mistakes

<AccordionGroup>
  <Accordion title="Empty set syntax">
    ```python theme={null}
    # Wrong - creates empty dict
    empty = {}

    # Right - use set()
    empty = set()
    ```
  </Accordion>

  <Accordion title="Sets are unordered">
    ```python theme={null}
    # Order is not guaranteed!
    numbers = {3, 1, 4, 1, 5}
    print(numbers)  # Could be any order

    # Use list if order matters
    ordered = [3, 1, 4, 1, 5]
    ```
  </Accordion>
</AccordionGroup>

## What's next?

Congratulations! You've completed Python Basics. Ready to start building programs?

<Card title="Building Programs" icon="graduation-cap" href="/functions">
  Learn about functions
</Card>