langchain-python-quickstart

# LangChain Python quickstart Follow the live docs — do not invent an alternate API from memory: **https://docs.langchain.com/oss/python/langchain/quickstart** Fetch that page (Docs MCP or HTTP) and implement what it shows (weather agent + `create_agent`). ## Local setup constraints Apply these on top of the quickstart (they keep setup minimal and model-agnostic): 1. **Ask** which provider/model to use. Showcase that LangChain is model-agnostic. Suggested prompt: > Which model should this agent use? Pass a `provider:model` string — e.g. `openai:gpt-5.5`, `anthropic:claude-sonnet-5`, `google_genai:gemini-2.5-flash-lite`. Default if you're unsure: **`anthropic:claude-sonnet-5`**. Swap the quickstart's model string for their choice (or the default). 2. Create a **new** directory (e.g. `langchain-agent/`) and do all work there — do not pollute the open project. 3. Only secret: the provider API key in `.env` (gitignored). No LangSmith / Tavily unless they ask. Prefer they edit `.env` themselves — don't paste keys into chat. 4. Install the provider package needed for their model if the quickstart's base install isn't enough. 5. Run the example, show output, then stop. Point to `langchain-fundamentals` for next steps.