# runnables

> **Module** in `langchain_classic`

📖 [View in docs](https://reference.langchain.com/python/langchain-classic/runnables)

LangChain **Runnable** and the **LangChain Expression Language (LCEL)**.

The LangChain Expression Language (LCEL) offers a declarative method to build
production-grade programs that harness the power of LLMs.

Programs created using LCEL and LangChain Runnables inherently support
synchronous, asynchronous, batch, and streaming operations.

Support for **async** allows servers hosting the LCEL based programs
to scale better for higher concurrent loads.

**Batch** operations allow for processing multiple inputs in parallel.

**Streaming** of intermediate outputs, as they're being generated, allows for
creating more responsive UX.

This module contains non-core Runnable classes.

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[View source on GitHub](https://github.com/langchain-ai/langchain/blob/c59e83a1ffba63d709ea4847445845edd82085dc/libs/langchain/langchain_classic/runnables/__init__.py)