Introduction to LangGraph Functions

LangGraph is an exciting new framework that brings stateful capabilities to language model applications. At the heart of LangGraph are its functions, which allow developers to create complex, stateful workflows with ease. In this blog post, we'll explore how to leverage these functions to build powerful and flexible AI systems.

The Basics of LangGraph Functions

LangGraph functions are the building blocks of your stateful workflows. They represent individual steps or actions in your application's logic. Each function takes in a state and returns a new state, allowing you to maintain context throughout your application's execution.

Here's a simple example of a LangGraph function:

from langgraph.prelude import *

@function
def greet(state):
    name = state["name"]
    state["greeting"] = f"Hello, {name}!"
    return state

In this example, the greet function takes a state containing a name and adds a greeting to the state.

Creating Stateful Workflows

The real power of LangGraph functions comes from combining them into workflows. Let's create a more complex example:

from langgraph.prelude import *

@function
def get_user_info(state):
    # Simulating user input
    state["name"] = "Alice"
    state["age"] = 30
    return state

@function
def calculate_birth_year(state):
    current_year = 2023
    state["birth_year"] = current_year - state["age"]
    return state

@function
def generate_message(state):
    name = state["name"]
    birth_year = state["birth_year"]
    state["message"] = f"Hello, {name}! You were born in {birth_year}."
    return state

workflow = StateGraph()
workflow.add_node("get_user_info", get_user_info)
workflow.add_node("calculate_birth_year", calculate_birth_year)
workflow.add_node("generate_message", generate_message)

workflow.add_edge("get_user_info", "calculate_birth_year")
workflow.add_edge("calculate_birth_year", "generate_message")

result = workflow.run({})
print(result["message"])

This workflow demonstrates how LangGraph functions can be chained together to create a more complex application. The state is passed from one function to the next, allowing each step to build upon the previous ones.

Advanced Features of LangGraph Functions

Conditional Branching

LangGraph functions support conditional branching, allowing your workflows to make decisions based on the current state:

@function
def check_age(state):
    if state["age"] >= 18:
        return "adult"
    else:
        return "minor"

workflow.add_node("check_age", check_age)
workflow.add_edge("get_user_info", "check_age")
workflow.add_conditional_edge("check_age", "adult_workflow", lambda x: x == "adult")
workflow.add_conditional_edge("check_age", "minor_workflow", lambda x: x == "minor")

Parallel Execution

You can also execute functions in parallel for improved performance:

workflow.add_parallel_nodes(["function1", "function2", "function3"])

This allows multiple independent operations to be performed simultaneously, potentially speeding up your application.

Integrating with Language Models

One of the most powerful aspects of LangGraph is its ability to seamlessly integrate with language models. Here's an example of how you might use a language model within a LangGraph function:

from langgraph.prelude import *
from langchain import OpenAI

llm = OpenAI()

@function
def generate_story(state):
    prompt = f"Write a short story about a person named {state['name']} who was born in {state['birth_year']}."
    state["story"] = llm(prompt)
    return state

workflow.add_node("generate_story", generate_story)
workflow.add_edge("generate_message", "generate_story")

This function uses the OpenAI language model to generate a story based on the user's information, seamlessly integrating AI capabilities into your workflow.

Conclusion

LangGraph functions provide a powerful and flexible way to create stateful workflows in Python. By combining these functions with language models, you can build sophisticated AI applications that maintain context and make intelligent decisions. As you continue to explore LangGraph, you'll discover even more ways to enhance your AI systems and create truly dynamic, stateful applications.