docs/langchain/templates/neo4j-cypher/README.md

# neo4j_cypher

This template allows you to interact with a Neo4j graph database in natural language, using an OpenAI LLM. 

It transforms a natural language question into a Cypher query (used to fetch data from Neo4j databases), executes the query, and provides a natural language response based on the query results.

[![Diagram showing the workflow of a user asking a question, which is processed by a Cypher generating chain, resulting in a Cypher query to the Neo4j Knowledge Graph, and then an answer generating chain that provides a generated answer based on the information from the graph.](https://raw.githubusercontent.com/langchain-ai/langchain/master/templates/neo4j-cypher/static/workflow.png "Neo4j Cypher Workflow Diagram")](https://medium.com/neo4j/langchain-cypher-search-tips-tricks-f7c9e9abca4d)

## Environment Setup

Define the following environment variables:

```
OPENAI_API_KEY=<YOUR_OPENAI_API_KEY>
NEO4J_URI=<YOUR_NEO4J_URI>
NEO4J_USERNAME=<YOUR_NEO4J_USERNAME>
NEO4J_PASSWORD=<YOUR_NEO4J_PASSWORD>
```

## Neo4j database setup

There are a number of ways to set up a Neo4j database.

### Neo4j Aura

Neo4j AuraDB is a fully managed cloud graph database service.
Create a free instance on [Neo4j Aura](https://neo4j.com/cloud/platform/aura-graph-database?utm_source=langchain&utm_content=langserve).
When you initiate a free database instance, you'll receive credentials to access the database.

## Populating with data

If you want to populate the DB with some example data, you can run `python ingest.py`.
This script will populate the database with sample movie data.

## Usage

To use this package, you should first have the LangChain CLI installed:

```shell
pip install -U langchain-cli
```

To create a new LangChain project and install this as the only package, you can do:

```shell
langchain app new my-app --package neo4j-cypher
```

If you want to add this to an existing project, you can just run:

```shell
langchain app add neo4j-cypher
```

And add the following code to your `server.py` file:
```python
from neo4j_cypher import chain as neo4j_cypher_chain

add_routes(app, neo4j_cypher_chain, path="/neo4j-cypher")
```

(Optional) Let's now configure LangSmith. 
LangSmith will help us trace, monitor and debug LangChain applications. 
You can sign up for LangSmith [here](https://smith.langchain.com/). 
If you don't have access, you can skip this section

```shell
export LANGCHAIN_TRACING_V2=true
export LANGCHAIN_API_KEY=<your-api-key>
export LANGCHAIN_PROJECT=<your-project>  # if not specified, defaults to "default"
```

If you are inside this directory, then you can spin up a LangServe instance directly by:

```shell
langchain serve
```

This will start the FastAPI app with a server is running locally at 
[http://localhost:8000](http://localhost:8000)

We can see all templates at [http://127.0.0.1:8000/docs](http://127.0.0.1:8000/docs)
We can access the playground at [http://127.0.0.1:8000/neo4j_cypher/playground](http://127.0.0.1:8000/neo4j_cypher/playground)  

We can access the template from code with:

```python
from langserve.client import RemoteRunnable

runnable = RemoteRunnable("http://localhost:8000/neo4j-cypher")
```