> ## 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.

# Error handling

> Handle errors gracefully

## What is error handling?

Errors happen. Files might not exist, APIs might be down, users might enter invalid data. Error handling lets your program deal with these problems gracefully instead of crashing.

## Where do errors come from?

**Errors you make** as a programmer:

* Typos and syntax mistakes (VS Code shows yellow squiggly lines)
* Logic errors like dividing by zero (only show up when code runs)
* Using variables before defining them
* Calling methods that don't exist

**Errors beyond your control**:

* User enters "abc" when you need a number
* File gets deleted after your program starts
* Internet connection drops during API call
* External service returns unexpected data

You might think "why not just write correct code?" But even perfect code needs error handling because the world is unpredictable. Users do unexpected things, networks fail, and files disappear.

## Types of errors

**Syntax errors** happen when Python can't understand your code:

```python theme={null}
# Missing colon
if x > 5  # SyntaxError
    print("Big number")
```

**Runtime errors** happen when your code runs:

```python theme={null}
# Division by zero
result = 10 / 0  # ZeroDivisionError

# Variable doesn't exist
print(score)  # NameError

# Wrong type
"hello" + 5  # TypeError
```

## Why handle errors?

Here's a program that crashes:

```python theme={null}
# This will crash if the file doesn't exist
with open('data.txt', 'r') as f:
    content = f.read()
print("Done!")  # Never reaches here if file missing
```

Here's a program that handles the error:

```python theme={null}
# This keeps running even if file doesn't exist
try:
    with open('data.txt', 'r') as f:
        content = f.read()
except FileNotFoundError:
    print("Could not find data.txt")
    content = "default data"
print("Done!")  # Always reaches here
```

<CardGroup cols={2}>
  <Card title="Try and except" icon="shield" href="/advanced/error-handling/try-except">
    Basic error handling syntax
  </Card>

  <Card title="Common errors" icon="bug" href="/advanced/error-handling/common-errors">
    Errors you'll encounter often
  </Card>
</CardGroup>