LangChain primitives – chains and runnables

As we have discussed, LangChain is a framework for orchestrating your generative AI applications. Let’s look at two key LangChain primitives: runnables and chains.

The most basic LangChain abstract interface is langchain_core/runnables/base.Runnable, and it makes it easy to compose different pieces together for the orchestration [4]. A Runnable defines three main methods (there are some more, mainly for asynchronous applications; you can take a look at the full documentation if you’re interested [4]):

• invoke calls Runnable on an input. It’s an abstract method that should be defined by the specific implementation.
• stream calls Runnable on an input and streams chunks of the response. With a default implementation, it just calls the invoke method and yields the output, but if you need proper streaming support, your Runnable should implement this method.
• batch calls Runnable on a list of inputs ...