Home Programming A Full Information to LangChain in Python — SitePoint

A Full Information to LangChain in Python — SitePoint

A Full Information to LangChain in Python — SitePoint


LangChain is a versatile Python library that empowers builders and researchers to create, experiment with, and analyze language fashions and brokers. It affords a wealthy set of options for pure language processing (NLP) fans, from constructing customized fashions to manipulating textual content information effectively. On this complete information, we’ll dive deep into the important elements of LangChain and display easy methods to harness its energy in Python.

Desk of Contents

Getting Set Up

To comply with together with this text, create a brand new folder and set up LangChain and OpenAI utilizing pip:

pip3 set up langchain openai


In LangChain, an Agent is an entity that may perceive and generate textual content. These brokers might be configured with particular behaviors and information sources and skilled to carry out varied language-related duties, making them versatile instruments for a variety of purposes.

Making a LangChain agent

Brokers might be configured to make use of “instruments” to collect the information they want and formulate a great response. Check out the instance beneath. It makes use of Serp API (an web search API) to look the Web for data related to the query or enter, and makes use of that to make a response. It additionally makes use of the llm-math software to carry out mathematical operations — for instance, to transform models or discover the proportion change between two values:

from langchain.brokers import load_tools
from langchain.brokers import initialize_agent
from langchain.brokers import AgentType
from langchain.llms import OpenAI
import os


OpenAI.api_key = "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"
llm = OpenAI(mannequin="gpt-3.5-turbo", temperature=0)
instruments = load_tools(["serpapi", "llm-math"], llm=llm)
agent = initialize_agent(instruments, llm, agent=AgentType.ZERO_SHOT_REACT_DESCRIPTION, verbose=True)
agent.run("How a lot power did wind generators produce worldwide in 2022?")

As you possibly can see, after doing all the fundamental importing and initializing our LLM (llm = OpenAI(mannequin="gpt-3.5-turbo", temperature=0)), the code masses the instruments essential for our agent to work utilizing instruments = load_tools(["serpapi", "llm-math"], llm=llm). It then creates the agent utilizing the initialize_agent perform, giving it the required instruments, and it offers it the ZERO_SHOT_REACT_DESCRIPTION description, which implies that it’s going to don’t have any reminiscence of earlier questions.

Agent take a look at instance 1

Let’s take a look at this agent with the next enter:

"How a lot power did wind generators produce worldwide in 2022?"

Testing Agent

As you possibly can see, it makes use of the next logic:

  • seek for “wind turbine power manufacturing worldwide 2022” utilizing the Serp web search API
  • analyze the most effective end result
  • get any related numbers
  • convert 906 gigawatts to joules utilizing the llm-math software, since we requested for power, not energy

Agent take a look at instance 2

LangChain brokers aren’t restricted to looking out the Web. We are able to join virtually any information supply (together with our personal) to a LangChain agent and ask it questions concerning the information. Let’s strive making an agent skilled on a CSV dataset.

Obtain this Netflix motion pictures and TV reveals dataset from SHIVAM BANSAL on Kaggle and transfer it into your listing. Now add this code into a brand new Python file:

from langchain.llms import OpenAI
from langchain.chat_models import ChatOpenAI
from langchain.brokers.agent_types import AgentType
from langchain.brokers import create_csv_agent
import os


agent = create_csv_agent(

agent.run("In what number of motion pictures was Christian Bale casted")

This code calls the create_csv_agent perform and makes use of the netflix_titles.csv dataset. The picture beneath reveals our take a look at.

Testing CSV Agent

As proven above, its logic is to look within the solid column for all occurrences of “Christian Bale”.

We are able to additionally make a Pandas Dataframe agent like this:

from langchain.brokers import create_pandas_dataframe_agent
from langchain.chat_models import ChatOpenAI
from langchain.brokers.agent_types import AgentType
from langchain.llms import OpenAI
import pandas as pd
import os

df = pd.read_csv("netflix_titles.csv")

agent = create_pandas_dataframe_agent(OpenAI(temperature=0), df, verbose=True)

agent.run("In what 12 months have been probably the most comedy motion pictures launched?")

If we run it, we’ll see one thing just like the outcomes proven beneath.

Testing Pandas Dataframe agent Logic

Testing Pandas Dataframe answer

These are only a few examples. We are able to use virtually any API or dataset with LangChain.


There are three kinds of fashions in LangChain: LLMs, chat fashions, and textual content embedding fashions. Let’s discover each kind of mannequin with some examples.

Language mannequin

LangChain offers a manner to make use of language fashions in Python to provide textual content output primarily based on textual content enter. It’s not as advanced as a chat mannequin, and is used greatest with easy enter–output language duties. Right here’s an instance utilizing OpenAI:

from langchain.llms import OpenAI
import os

llm = OpenAI(mannequin="gpt-3.5-turbo", temperature=0.9)
print(llm("Give you a rap title for Matt Nikonorov"))

As seen above, it makes use of the gpt-3.5-turbo mannequin to generate an output for the supplied enter (“Give you a rap title for Matt Nikonorov”). On this instance, I’ve set the temperature to 0.9 to make the LLM actually artistic. It got here up with “MC MegaMatt”. I’d give that one a stable 9/10.

Chat mannequin

Making LLM fashions provide you with rap names is enjoyable, but when we would like extra refined solutions and conversations, we have to step up our sport through the use of a chat mannequin. How are chat fashions technically totally different from language fashions? Properly, within the phrases of the LangChain documentation:

Chat fashions are a variation on language fashions. Whereas chat fashions use language fashions beneath the hood, the interface they use is a bit totally different. Fairly than utilizing a “textual content in, textual content out” API, they use an interface the place “chat messages” are the inputs and outputs.

Right here’s a easy Python chat mannequin script:

from langchain.llms import OpenAI
from langchain.chat_models import ChatOpenAI
from langchain.schema import (
import os

chat = ChatOpenAI()
messages = [
    SystemMessage(content="You are a friendly, informal assistant"),
    HumanMessage(content="Convince me that Djokovic is better than Federer")

As proven above, the code first sends a SystemMessage and tells the chatbot to be pleasant and casual, and afterwards it sends a HumanMessage telling the chatbot to persuade us that Djokovich is best than Federer.

In case you run this chatbot mannequin, you’ll see one thing just like the end result proven beneath.

chatbot Model Test


Embeddings present a approach to flip phrases and numbers in a block of textual content into vectors that may then be related to different phrases or numbers. This may increasingly sound summary, so let’s take a look at an instance:

from langchain.embeddings import OpenAIEmbeddings

embeddings_model = OpenAIEmbeddings()
embedded_query = embeddings_model.embed_query("Who created the world vast net?")

This can return a listing of floats: [0.022762885317206383, -0.01276398915797472, 0.004815981723368168, -0.009435392916202545, 0.010824492201209068]. That is what an embedding appears like.

A use case of embedding fashions

If we need to practice a chatbot or LLM to reply questions associated to our information or to a selected textual content pattern, we have to use embeddings. Let’s make a easy CSV file (embs.csv) that has a “textual content” column containing three items of data:

textual content
"Robert Wadlow was the tallest human ever"
"The Burj Khalifa is the tallest skyscraper"
"Roses are pink"

Now right here’s a script that may take the query “Who was the tallest human ever?” and discover the suitable reply within the CSV file through the use of embeddings:

from langchain.embeddings import OpenAIEmbeddings
from openai.embeddings_utils import cosine_similarity
import os
import pandas

embeddings_model = OpenAIEmbeddings()

df = pandas.read_csv("embs.csv")

emb1 = embeddings_model.embed_query(df["text"][0])
emb2 = embeddings_model.embed_query(df["text"][1])
emb3 = embeddings_model.embed_query(df["text"][2])
emb_list = [emb1, emb2, emb3]
df["embedding"] = emb_list

embedded_question = embeddings_model.embed_query("Who was the tallest human ever?") 
df["similarity"] = df.embedding.apply(lambda x: cosine_similarity(x, embedded_question)) 
df2 = df.sort_values("similarity", ascending=False) 

If we run this code, we’ll see that it outputs “Robert Wadlow was the tallest human ever”. The code finds the suitable reply by getting the embedding of every piece of data and discovering the one most associated to the embedding of the query “Who was the tallest human ever?” The ability of embeddings!


LangChain fashions can’t deal with giant texts on the identical time and use them to make responses. That is the place chunks and textual content splitting are available in. Le’s take a look at two easy methods to separate our textual content information into chunks earlier than feeding it into LangChain.

Splitting chunks by character

To keep away from abrupt breaks in chunks, we will cut up our texts by paragraphs by splitting them at each prevalence of a newline or double-newline:

from langchain.text_splitter import RecursiveCharacterTextSplitter
text_splitter = RecursiveCharacterTextSplitter(separators=["nn", "n"], chunk_size=2000, chunk_overlap=250)
texts = text_splitter.split_text(your_text)

Recursively splitting chunks

If we need to strictly cut up our textual content by a sure size of characters, we will achieve this utilizing RecursiveCharacterTextSplitter:

from langchain.text_splitter import RecursiveCharacterTextSplitter
text_splitter = RecursiveCharacterTextSplitter(
texts = text_splitter.create_documents([your_text])

Chunk dimension and overlap

Whereas trying on the examples above, you might have questioned precisely what the chunk dimension and overlap parameters imply, and what implications they’ve on efficiency. That may be defined with two factors:

  • Chunk dimension decides the quantity of characters that can be in every chunk. The larger the chunk dimension, the extra information is within the chunk, and the extra time it’ll take LangChain to course of it and to provide an output, and vice versa.
  • Chunk overlap is what shares data between chunks in order that they share some context. The upper the chunk overlap, the extra redundant our chunks can be, the decrease the chunk overlap, and the much less context can be shared between the chunks. Typically, a great chunk overlap is between 10% and 20% of the chunk dimension, though the perfect chunk overlap varies throughout totally different textual content varieties and use instances.


Chains are principally a number of LLM functionalities linked collectively to carry out extra advanced duties that couldn’t in any other case be performed with easy LLM enter --> output style. Let’s take a look at a cool instance:

from langchain.llms import OpenAI
from langchain.prompts import PromptTemplate
from langchain.chains import LLMChain
import os
os.environ["OPENAI_API_KEY"] = "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"

llm = OpenAI(temperature=0.9)
immediate = PromptTemplate(
    input_variables=["media", "topic"],
    template="What is an efficient title for a {media} about {subject}",
chain = LLMChain(llm=llm, immediate=immediate)
    'media': "horror film",
    'subject': "math"

This code takes two variables into its immediate and formulates a artistic reply (temperature=0.9). On this instance, we’ve requested it to provide you with a great title for a horror film about math. The output after working this code was “The Calculating Curse”, however this doesn’t actually present the complete energy of chains.

Let’s check out a extra sensible instance:

from langchain.chat_models import ChatOpenAI
from langchain.prompts import PromptTemplate
from typing import Elective

from langchain.chains.openai_functions import (
import os

os.environ["OPENAI_API_KEY"] = "YOUR_KEY"

llm = ChatOpenAI(mannequin="gpt-3.5-turbo", temperature=0.1)
template = """Use the given format to extract data from the next enter: {enter}. Make certain to reply within the right format"""

immediate = PromptTemplate(template=template, input_variables=["input"])

json_schema = {
    "kind": "object",
    "properties": {
        "title": {"title": "Title", "description": "The artist's title", "kind": "string"},
        "style": {"title": "Style", "description": "The artist's music style", "kind": "string"},
        "debut": {"title": "Debut", "description": "The artist's debut album", "kind": "string"},
        "debut_year": {"title": "Debut_year", "description": "12 months of artist's debut album", "kind": "integer"}
    "required": ["name", "genre", "debut", "debut_year"],

chain = create_structured_output_chain(json_schema, llm, immediate, verbose=False)
f = open("Nas.txt", "r")
artist_info = str(f.learn())

This code could look complicated, so let’s stroll by means of it.

This code reads a brief biography of Nas (Hip-Hop Artist) and extracts the next values from the textual content and codecs them right into a JSON object:

  • the artist’s title
  • the artist’s music style
  • the artist’s debut album
  • the 12 months of artist’s debut album

Within the immediate we additionally specify “Make certain to reply within the right format”, in order that we at all times get the output in JSON format. Right here’s the output of this code:

{'title': 'Nas', 'style': 'Hip Hop', 'debut': 'Illmatic', 'debut_year': 1994}

By offering a JSON schema to the create_structured_output_chain perform, we’ve made the chain put its output into JSON format.

Going Past OpenAI

Though I preserve utilizing OpenAI fashions as examples of the totally different functionalities of LangChain, it isn’t restricted to OpenAI fashions. We are able to use LangChain with a mess of different LLMs and AI companies. (Right here’s a full checklist of LangChain integratable LLMs.)

For instance, we will use Cohere with LangChain. Right here’s the documentation for the LangChain Cohere integration, however simply to present a sensible instance, after putting in Cohere utilizing pip3 set up cohere we will make a easy query --> reply code utilizing LangChain and Cohere like this:

from langchain.llms import Cohere
from langchain.prompts import PromptTemplate
from langchain.chains import LLMChain

template = """Query: {query}

Reply: Let's assume step-by-step."""

immediate = PromptTemplate(template=template, input_variables=["question"])
llm = Cohere(cohere_api_key="YOUR_COHERE_KEY")
llm_chain = LLMChain(immediate=immediate, llm=llm)

query = "When was Novak Djokovic born?"


The code above produces the next output:

The reply is Novak Djokovic was born on Could 22, 1987.

Novak Djokovic is a Serbian tennis participant.


On this information, you’ve seen the totally different facets and functionalities of LangChain. Armed with this data, you’re now geared up to leverage LangChain’s capabilities in your NLP endeavors, whether or not you’re a researcher, developer, or hobbyist.

You’ll find a repo with all the pictures and the Nas.txt file from this text on GitHub.

Pleased coding and experimenting with LangChain in Python!


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