LangChain Python Example

A sample script that uses LangChain to talk to LLMs.

Based on https://python.langchain.com/docs/tutorials/llm_chain/

You’ll need an API key for each LLM. So just follow the instructions linked below to obtain your API keys.

• OpenAI ChatGPT
• Anthropic Claude
• Google Gemini

Save the keys to the app/src/main/resources/.env file as the corresponding ..._API_KEY environment variable. You can use app/src/main/resources/.env.template as a guide to structure your .env file.

Environment

(Re)create the Virtual Environment

python3 -m venv .venv
. .venv/bin/activate
pip install langsmith
conda create --name langchain
conda install --name langchain --file requirements.txt --channel conda-forge

Activate the Virtual Environment

. .venv/bin/activate
conda activate langchain

To Run

The sample logic is in the file main.py.

To run against OpenAI's ChatGPT:

python main.py --model openai

To run against Anthropic's Claude:

python main.py --model anthropic

To run against Google's Gemini:

python main.py --model google

To run against DeekSeek's R1:

python main.py --model deepseek

If you don't specify --model, it will default to openai and use ChatGPT.