---
title: Langchain
description: Use LangChain Python packages to build AI applications on Cloudflare Workers.
image: https://developers.cloudflare.com/dev-products-preview.png
---

> Documentation Index  
> Fetch the complete documentation index at: https://developers.cloudflare.com/workers/llms.txt  
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# Langchain

[LangChain ↗](https://www.langchain.com/) is the most popular framework for building AI applications powered by large language models (LLMs).

LangChain publishes multiple Python packages. The following are provided by the Workers runtime:

* [langchain ↗](https://pypi.org/project/langchain/) (version `0.1.8`)
* [langchain-core ↗](https://pypi.org/project/langchain-core/) (version `0.1.25`)
* [langchain-openai ↗](https://pypi.org/project/langchain-openai/) (version `0.0.6`)

## Get Started

Clone the `cloudflare/python-workers-examples` repository and run the LangChain example:

Terminal window

```

git clone https://github.com/cloudflare/python-workers-examples

cd 05-langchain

uv run pywrangler dev


```

### Example code

Python

```

from workers import WorkerEntrypoint, Response

from langchain_core.prompts import PromptTemplate

from langchain_openai import OpenAI


class Default(WorkerEntrypoint):

    async def fetch(self, request):

        prompt = PromptTemplate.from_template("Complete the following sentence: I am a {profession} and ")

        llm = OpenAI(api_key=self.env.API_KEY)

        chain = prompt | llm


        res = await chain.ainvoke({"profession": "electrician"})

        return Response(res.split(".")[0].strip())


```

```json
{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/directory/","name":"Directory"}},{"@type":"ListItem","position":2,"item":{"@id":"/workers/","name":"Workers"}},{"@type":"ListItem","position":3,"item":{"@id":"/workers/languages/","name":"Languages"}},{"@type":"ListItem","position":4,"item":{"@id":"/workers/languages/python/","name":"Python Workers"}},{"@type":"ListItem","position":5,"item":{"@id":"/workers/languages/python/packages/","name":"Packages"}},{"@type":"ListItem","position":6,"item":{"@id":"/workers/languages/python/packages/langchain/","name":"Langchain"}}]}
```