How do I use the Claude API in a Python project?

First, sign up at console.anthropic.com and generate an API key. Then install the official SDK with pip install anthropic. Set your key as an environment variable: export ANTHROPIC_API_KEY=your_key_here. Then in Python you can do: import anthropic; client = anthropic.Anthropic(); message = client.messages.create(model="claude-opus-4-5", max_tokens=1024, messages=[{"role":"user","content":"Hello Claude"}]); print(message.content). That is all you need for a basic call.

Always store your API key in an environment variable or a secrets manager — never hardcode it in your source files. Use python-dotenv to load it from a .env file during development. For production apps on AWS or GCP, use their native secrets services instead.

Pay attention to the model string you pass in. Current model identifiers for the Claude 4 family are claude-opus-4-5 and claude-sonnet-4-5. Check the Anthropic docs at docs.anthropic.com regularly as new model versions are released frequently and older identifiers may be deprecated over time.