# Using the Anthropic Python SDK

## Installation

```
pip install anthropic
```

## Creating a client

```python
import anthropic

client = anthropic.Anthropic()
```

If you don't pass `api_key` explicitly, the client reads it from the
`ANTHROPIC_API_KEY` environment variable.

## Sending a message

```python
message = client.messages.create(
    model="claude-sonnet-5",
    max_tokens=1024,
    messages=[{"role": "user", "content": "Hello, world"}],
)
```

If you omit `max_tokens`, it defaults to 1024.

## Automatic retries

By default, the client automatically retries a failed request up to 5 times
before raising an error.

## Streaming responses

You can stream a response incrementally using `client.messages.stream_response()`
as a context manager, rather than waiting for the full response to complete.

## Async usage

For async code, use `anthropic.AsyncAnthropic()` instead. It mirrors the same
methods as the synchronous client, but you `await` them.