# Comprehensive Guide to Using Claude 3.5 Sonnet API

## Table of Contents
1. [Introduction](#introduction)
2. [Installation](#installation)
3. [API Key Setup](#api-key-setup)
4. [Basic Usage](#basic-usage)
5. [Advanced Usage](#advanced-usage)
6. [Streaming Responses](#streaming-responses)
7. [Error Handling](#error-handling)
8. [Best Practices](#best-practices)
9. [Troubleshooting](#troubleshooting)

## Introduction

Claude 3.5 Sonnet is the most intelligent model in the Claude 3.5 family, combining top-tier performance with improved speed. It excels in:

- Advanced research and analysis
- Complex problem-solving
- Sophisticated language understanding and generation
- High-level strategic planning

## Installation

Install the Anthropic Python library:

```bash
pip install anthropic
```

Ensure you have Python 3.7 or higher installed.

## API Key Setup

Set your API key as an environment variable:

```bash
export ANTHROPIC_API_KEY='your-api-key-here'
```

Alternatively, you can pass it directly when initializing the client:

```python
from anthropic import Anthropic

client = Anthropic(api_key='your-api-key-here')
```

## Basic Usage

Here's a basic example of using Claude 3.5 Sonnet:

```python
import anthropic

client = anthropic.Anthropic()

message = client.messages.create(
    model="claude-3-5-sonnet-20240620",
    max_tokens=1000,
    temperature=0,
    system="You are a world-class poet. Respond only with short poems.",
    messages=[
        {
            "role": "user",
            "content": [
                {
                    "type": "text",
                    "text": "Why is the ocean salty?"
                }
            ]
        }
    ]
)
print(message.content)
```

Key parameters:
- `model`: Always use `"claude-3-5-sonnet-20240620"` for this model.
- `max_tokens`: Limits the length of the response.
- `temperature`: Controls randomness (0 for deterministic responses).
- `system`: Sets instructions or persona for Claude.
- `messages`: List of message objects with `role` and `content`.

## Advanced Usage

### Async Usage

For asynchronous operations:

```python
from anthropic import AsyncAnthropic
import asyncio

client = AsyncAnthropic()

async def main():
    message = await client.messages.create(
        model="claude-3-5-sonnet-20240620",
        max_tokens=1000,
        messages=[{"role": "user", "content": "Hello, Claude"}],
    )
    print(message.content)

asyncio.run(main())
```

### Token Counting

Monitor token usage:

```python
message = client.messages.create(...)
print(message.usage)  # Usage(input_tokens=25, output_tokens=13)
```

## Streaming Responses

Stream responses for real-time output:

```python
stream = client.messages.create(
    model="claude-3-5-sonnet-20240620",
    max_tokens=1000,
    messages=[{"role": "user", "content": "Tell me a story"}],
    stream=True,
)
for event in stream:
    print(event.type)
    if event.type == 'content_block_delta':
        print(event.delta.text, end='', flush=True)
```

## Error Handling

Implement robust error handling:

```python
import anthropic
from anthropic import Anthropic

client = Anthropic()

try:
    message = client.messages.create(
        model="claude-3-5-sonnet-20240620",
        max_tokens=1000,
        messages=[{"role": "user", "content": "Hello, Claude"}],
    )
except anthropic.APIConnectionError as e:
    print("Connection error:", e)
except anthropic.RateLimitError as e:
    print("Rate limit exceeded. Retrying after a delay...")
except anthropic.APIStatusError as e:
    print(f"API error: {e.status_code}")
    print(e.response)
except anthropic.APIError as e:
    print("Unexpected error:", e)
```

## Best Practices

1. Use system prompts to control Claude's behavior and output format.
2. Keep messages concise and clear for optimal performance.
3. Use appropriate `max_tokens` to control response length.
4. Implement proper error handling and retries for production use.
5. Use streaming for long responses or real-time interactions.
6. Monitor and optimize token usage to manage costs.

## Troubleshooting

- If experiencing connection issues, check your internet connection and API key validity.
- For rate limit errors, implement exponential backoff in your retry logic.
- Enable debug logging for detailed information:
  ```bash
  export ANTHROPIC_LOG=debug
  ```
- For unexpected behavior, verify you're using the correct model version and parameters.

Remember to always refer to the [official Anthropic documentation](https://docs.anthropic.com) for the most up-to-date information on Claude 3.5 Sonnet and its capabilities.