Estimated reading time: 5 minutes
Table of contents
Introduction to LangGraph
LangGraph is a powerful framework by LangChain designed for creating stateful, multi-actor applications with LLMs. It provides the structure and tools needed to build sophisticated AI agents through a graph-based approach.
Think of LangGraph as an architect’s drafting table – it gives us the tools to design how our agent will think and act. Just as an architect draws blueprints showing how different rooms connect and how people will flow through a building, LangGraph lets us design how different capabilities will connect and how information will flow through our agent.
Key Features:
- State Management: Maintain persistent state across interactionsFlexible Routing: Define complex flows between componentsPersistence: Save and resume workflowsVisualization: See and understand your agent’s structure
In this tutorial, we’ll demonstrate LangGraph by building a multi-step text analysis pipeline that processes text through three stages:
- Text Classification: Categorize input text into predefined categoriesEntity Extraction: Identify key entities from the textText Summarization: Generate a concise summary of the input text
This pipeline showcases how LangGraph can be used to create a modular, extensible workflow for natural language processing tasks.
Setting Up Our Environment
Before diving into the code, let’s set up our development environment.
Installation
# Install required packages!pip install langgraph langchain langchain-openai python-dotenvSetting Up API Keys
We’ll need an OpenAI API key to use their models. If you haven’t already, you can get one from https://platform.openai.com/signup.
Check out the Full Codes here
import osfrom dotenv import load_dotenv# Load environment variables from .env file (create this with your API key)load_dotenv()# Set OpenAI API keyos.environ["OPENAI_API_KEY"] = os.getenv('OPENAI_API_KEY')Testing Our Setup
Let’s make sure our environment is working correctly by creating a simple test with the OpenAI model:
from langchain_openai import ChatOpenAI# Initialize the ChatOpenAI instancellm = ChatOpenAI(model="gpt-4o-mini")# Test the setupresponse = llm.invoke("Hello! Are you working?")print(response.content)Building Our Text Analysis Pipeline
Now let’s import the necessary packages for our LangGraph text analysis pipeline:
import osfrom typing import TypedDict, List, Annotatedfrom langgraph.graph import StateGraph, ENDfrom langchain.prompts import PromptTemplatefrom langchain_openai import ChatOpenAIfrom langchain.schema import HumanMessagefrom langchain_core.runnables.graph import MermaidDrawMethodfrom IPython.display import display, ImageDesigning Our Agent’s Memory
Just as human intelligence requires memory, our agent needs a way to keep track of information. We create this using a TypedDict to define our state structure: Check out the Full Codes here
class State(TypedDict): text: str classification: str entities: List[str] summary: str# Initialize our language model with temperature=0 for more deterministic outputsllm = ChatOpenAI(model="gpt-4o-mini", temperature=0)Creating Our Agent’s Core Capabilities
Now we’ll create the actual skills our agent will use. Each of these capabilities is implemented as a function that performs a specific type of analysis. Check out the Full Codes here
1. Classification Node
def classification_node(state: State): '''Classify the text into one of the categories: News, Blog, Research, or Other''' prompt = PromptTemplate( input_variables=["text"], template="Classify the following text into one of the categories: News, Blog, Research, or Other.\n\nText:{text}\n\nCategory:" ) message = HumanMessage(content=prompt.format(text=state["text"])) classification = llm.invoke([message]).content.strip() return {"classification": classification}2. Entity Extraction Node
def entity_extraction_node(state: State): '''Extract all the entities (Person, Organization, Location) from the text''' prompt = PromptTemplate( input_variables=["text"], template="Extract all the entities (Person, Organization, Location) from the following text. Provide the result as a comma-separated list.\n\nText:{text}\n\nEntities:" ) message = HumanMessage(content=prompt.format(text=state["text"])) entities = llm.invoke([message]).content.strip().split(", ") return {"entities": entities}3. Summarization Node
def summarization_node(state: State): '''Summarize the text in one short sentence''' prompt = PromptTemplate( input_variables=["text"], template="Summarize the following text in one short sentence.\n\nText:{text}\n\nSummary:" ) message = HumanMessage(content=prompt.format(text=state["text"])) summary = llm.invoke([message]).content.strip() return {"summary": summary}Bringing It All Together
Now comes the most exciting part – connecting these capabilities into a coordinated system using LangGraph:
Check out the Full Codes here
# Create our StateGraphworkflow = StateGraph(State)# Add nodes to the graphworkflow.add_node("classification_node", classification_node)workflow.add_node("entity_extraction", entity_extraction_node)workflow.add_node("summarization", summarization_node)# Add edges to the graphworkflow.set_entry_point("classification_node") # Set the entry point of the graphworkflow.add_edge("classification_node", "entity_extraction")workflow.add_edge("entity_extraction", "summarization")workflow.add_edge("summarization", END)# Compile the graphapp = workflow.compile()Workflow Structure: Our pipeline follows this path:
classification_node → entity_extraction → summarization → END
Testing Our Agent
Now that we’ve built our agent, let’s see how it performs with a real-world text example:
Check out the Full Codes here
sample_text = """ OpenAI has announced the GPT-4 model, which is a large multimodal model that exhibits human-level performance on various professional benchmarks. It is developed to improve the alignment and safety of AI systems. Additionally, the model is designed to be more efficient and scalable than its predecessor, GPT-3. The GPT-4 model is expected to be released in the coming months and will be available to the public for research and development purposes. """ state_input = {"text": sample_text} result = app.invoke(state_input) print("Classification:", result["classification"]) print("\nEntities:", result["entities"]) print("\nSummary:", result["summary"])Classification: News Entities: ['OpenAI', 'GPT-4', 'GPT-3'] Summary: OpenAI's upcoming GPT-4 model is a multimodal AI that aims for human-level performance and improved safety, efficiency, and scalability compared to GPT-3.Understanding the Power of Coordinated Processing
What makes this result particularly impressive isn’t just the individual outputs – it’s how each step builds on the others to create a complete understanding of the text.
- The classification provides context that helps frame our understanding of the text typeThe entity extraction identifies important names and conceptsThe summarization distills the essence of the document
This mirrors human reading comprehension, where we naturally form an understanding of what kind of text it is, note important names and concepts, and form a mental summary – all while maintaining the relationships between these different aspects of understanding.
Try with Your Own Text
Now let’s try our pipeline with another text sample:
Check out the Full Codes here
# Replace this with your own text to analyze your_text = """ The recent advancements in quantum computing have opened new possibilities for cryptography and data security. Researchers at MIT and Google have demonstrated quantum algorithms that could potentially break current encryption methods. However, they are also developing new quantum-resistant encryption techniques to protect data in the future. """ # Process the text through our pipeline your_result = app.invoke({"text": your_text}) print("Classification:", your_result["classification"]) print("\nEntities:", your_result["entities"]) print("\nSummary:", your_result["summary"])Classification: Research Entities: ['MIT', 'Google'] Summary: Recent advancements in quantum computing may threaten current encryption methods while also prompting the development of new quantum-resistant techniques.Adding More Capabilities (Advanced)
One of the powerful aspects of LangGraph is how easily we can extend our agent with new capabilities. Let’s add a sentiment analysis node to our pipeline:
Check out the Full Codes here
# First, let's update our State to include sentimentclass EnhancedState(TypedDict): text: str classification: str entities: List[str] summary: str sentiment: str# Create our sentiment analysis nodedef sentiment_node(state: EnhancedState): '''Analyze the sentiment of the text: Positive, Negative, or Neutral''' prompt = PromptTemplate( input_variables=["text"], template="Analyze the sentiment of the following text. Is it Positive, Negative, or Neutral?\n\nText:{text}\n\nSentiment:" ) message = HumanMessage(content=prompt.format(text=state["text"])) sentiment = llm.invoke([message]).content.strip() return {"sentiment": sentiment}# Create a new workflow with the enhanced stateenhanced_workflow = StateGraph(EnhancedState)# Add the existing nodesenhanced_workflow.add_node("classification_node", classification_node)enhanced_workflow.add_node("entity_extraction", entity_extraction_node)enhanced_workflow.add_node("summarization", summarization_node)# Add our new sentiment nodeenhanced_workflow.add_node("sentiment_analysis", sentiment_node)# Create a more complex workflow with branchesenhanced_workflow.set_entry_point("classification_node")enhanced_workflow.add_edge("classification_node", "entity_extraction")enhanced_workflow.add_edge("entity_extraction", "summarization")enhanced_workflow.add_edge("summarization", "sentiment_analysis")enhanced_workflow.add_edge("sentiment_analysis", END)# Compile the enhanced graphenhanced_app = enhanced_workflow.compile()Testing the Enhanced Agent
# Try the enhanced pipeline with the same textenhanced_result = enhanced_app.invoke({"text": sample_text})print("Classification:", enhanced_result["classification"])print("\nEntities:", enhanced_result["entities"])print("\nSummary:", enhanced_result["summary"])print("\nSentiment:", enhanced_result["sentiment"])Classification: NewsEntities: ['OpenAI', 'GPT-4', 'GPT-3']Summary: OpenAI's upcoming GPT-4 model is a multimodal AI that aims for human-level performance and improved safety, efficiency, and scalability compared to GPT-3.Sentiment: The sentiment of the text is Positive. It highlights the advancements and improvements of the GPT-4 model, emphasizing its human-level performance, efficiency, scalability, and the positive implications for AI alignment and safety. The anticipation of its release for public use further contributes to the positive tone.
Adding Conditional Edges (Advanced Logic)
Why Conditional Edges?
So far, our graph has followed a fixed linear path: classification_node → entity_extraction → summarization → (sentiment)
But in real-world applications, we often want to run certain steps only if needed. For example:
- Only extract entities if the text is a News or Research articleSkip summarization if the text is very shortAdd custom processing for Blog posts
LangGraph makes this easy through conditional edges – logic gates that dynamically route execution based on data in the current state.
Check out the Full Codes here
Creating a Routing Function
# Route after classificationdef route_after_classification(state: EnhancedState) -> str: category = state["classification"].lower() # returns: "news", "blog", "research", "other" return category in ["news", "research"]Define the Conditional Graph
from langgraph.graph import StateGraph, ENDconditional_workflow = StateGraph(EnhancedState)# Add nodesconditional_workflow.add_node("classification_node", classification_node)conditional_workflow.add_node("entity_extraction", entity_extraction_node)conditional_workflow.add_node("summarization", summarization_node)conditional_workflow.add_node("sentiment_analysis", sentiment_node)# Set entry pointconditional_workflow.set_entry_point("classification_node")# Add conditional edgeconditional_workflow.add_conditional_edges("classification_node", route_after_classification, path_map={ True: "entity_extraction", False: "summarization"})# Add remaining static edgesconditional_workflow.add_edge("entity_extraction", "summarization")conditional_workflow.add_edge("summarization", "sentiment_analysis")conditional_workflow.add_edge("sentiment_analysis", END)# Compileconditional_app = conditional_workflow.compile()Testing the Conditional Pipeline
test_text = """OpenAI released the GPT-4 model with enhanced performance on academic and professional tasks. It's seen as a major breakthrough in alignment and reasoning capabilities."""result = conditional_app.invoke({"text": test_text})print("Classification:", result["classification"])print("Entities:", result.get("entities", "Skipped"))print("Summary:", result["summary"])print("Sentiment:", result["sentiment"])Classification: NewsEntities: ['OpenAI', 'GPT-4']Summary: OpenAI's GPT-4 model significantly improves performance in academic and professional tasks, marking a breakthrough in alignment and reasoning.Sentiment: The sentiment of the text is Positive. It highlights the release of the GPT-4 model as a significant advancement, emphasizing its enhanced performance and breakthrough capabilities.
Check out the Full Codes here
Now try it with a Blog:
blog_text = """Here's what I learned from a week of meditating in silence. No phones, no talking—just me, my breath, and some deep realizations."""result = conditional_app.invoke({"text": blog_text})print("Classification:", result["classification"])print("Entities:", result.get("entities", "Skipped (not applicable)"))print("Summary:", result["summary"])print("Sentiment:", result["sentiment"])Classification: BlogEntities: Skipped (not applicable)Summary: A week of silent meditation led to profound personal insights.Sentiment: The sentiment of the text is Positive. The mention of "deep realizations" and the overall reflective nature of the experience suggests a beneficial and enlightening outcome from the meditation practice.
With conditional edges, our agent can now:
- Make decisions based on contextSkip unnecessary stepsRun faster and cheaperBehave more intelligently
Conclusion
In this tutorial, we’ve:
- Explored LangGraph concepts and its graph-based approachBuilt a text processing pipeline with classification, entity extraction, and summarizationEnhanced our pipeline with additional capabilitiesIntroduced conditional edges to dynamically control the flow based on classification resultsVisualized our workflowTested our agent with real-world text examples
LangGraph provides a powerful framework for creating AI agents by modeling them as graphs of capabilities. This approach makes it easy to design, modify, and extend complex AI systems.
Next Steps
- Add more nodes to extend your agent’s capabilitiesExperiment with different LLMs and parametersExplore LangGraph’s state persistence features for ongoing conversations
Check out the Full Codes here. All credit for this research goes to the researchers of this project. Also, feel free to follow us on Twitter and don’t forget to join our 100k+ ML SubReddit and Subscribe to our Newsletter.
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