langchain/templates/docs/LAUNCHING_PACKAGE.md

Launching LangServe from a Package

You can also launch LangServe directly from a package, without having to pull it into a project. This can be useful when you are developing a package and want to test it quickly. The downside of this is that it gives you a little less control over how the LangServe APIs are configured, which is why for proper projects we recommend creating a full project.

In order to do this, first change your working directory to the package itself. For example, if you are currently in this templates module, you can go into the pirate-speak package with:

cd pirate-speak

Inside this package there is a pyproject.toml file. This file contains a tool.langchain section that contains information on how this package should be used. For example, in pirate-speak we see:

[tool.langserve]
export_module = "pirate_speak.chain"
export_attr = "chain"

This information can be used to launch a LangServe instance automatically. In order to do this, first make sure the CLI is installed:

pip install -U langchain-cli

You can then run:

langchain template serve

This will spin up endpoints, documentation, and playground for this chain. For example, you can access the playground at http://127.0.0.1:8000/playground/