How to Master Resume Ranking with Langchain?

Pauline I C 20 Oct, 2023 • 11 min read


In the ever-evolving job market, employers often find themselves overwhelmed with a deluge of resumes for every job opening. The process of sifting through these resumes to identify the most qualified candidates can be time-consuming and daunting. To address this challenge, we will delve into the creation of a sophisticated resume ranking with Langchain, a robust language processing tool. This application will automatically filter resumes based on specified key skills and rank them according to their skill match.

Learning Objectives

  • Deep understanding of resume-ranking application development with Langchain
  • Streamline candidate evaluation process
  • Efficiently identify suitable job applicants

This article was published as a part of the Data Science Blogathon.

Significance of AI-Powered Resume Ranking

  • Time Saver: Think of AI as your time-saving assistant. It goes through heaps of resumes in seconds, so you don’t have to spend hours on it. This allows you to focus on other important tasks.
  • Smart Choices: AI isn’t just fast; it’s smart. It spots the resumes that match your job requirements perfectly. This helps you make better hiring decisions and find the right people faster.
  • Competitive Edge: In a world where job openings attract dozens, if not hundreds, of applicants, using AI gives you an edge. You’re not just keeping up with the competition; you’re leading the way in efficient and effective hiring.
  • Less Stress: Sorting through resumes can be stressful. AI takes the pressure off, making the hiring process smoother and more enjoyable for everyone involved.

So, let’s embark on this journey and discover how to create your own AI-powered resume-ranking tool step by step.

resume ranking with langchain

Setting the Stage

What is the Need for Resume Ranking?

The recruitment process is an integral part of any organization’s growth. However, with an increasing number of job applicants, sorting through resumes manually can be a time-intensive task prone to human errors. Resume ranking alleviates this burden by automating the process of identifying the most qualified candidates. This not only saves time but also ensures that no potential candidate is overlooked.

Introducing Langchain

Langchain is a comprehensive language processing tool that empowers developers to perform complex text analysis and information extraction tasks. Its capabilities include text splitting, embeddings, sequential search, and question-and-answer retrieval. By leveraging Langchain, we can automate the extraction of crucial information from resumes, making the ranking process more efficient.

The Role of Language Models in Resume Ranking

In the digital age, where vast amounts of textual data are generated daily, the ability to harness and understand language is of paramount importance. Language models, coupled with Natural Language Processing (NLP) techniques, have become instrumental in automating various text-related tasks. This section delves into the significance of language models, the importance of NLP, and how Langchain enhances NLP for resume ranking.

Understanding Language Models

Language models are computational systems designed to understand, generate, and manipulate human language. They are essentially algorithms that learn the structure, grammar, and semantics of a language by processing large volumes of text data. These models have evolved significantly, primarily due to advancements in deep learning and neural networks.

One key feature of modern language models is their ability to predict the probability of a word or phrase occurring in a given context. This predictive capability enables them to generate coherent and contextually relevant text. Language models like GPT-3, developed by OpenAI, have demonstrated remarkable proficiency in various natural language understanding tasks, making them a valuable tool for a wide range of applications.

The Importance of Natural Language Processing (NLP)

Natural Language Processing (NLP) is a subfield of artificial intelligence that focuses on enabling computers to understand, interpret, and generate human language in a valuable way. NLP applications are diverse, including machine translation, sentiment analysis, chatbots, and, crucially, resume ranking.

In the context of resume ranking, NLP empowers systems to extract meaningful information from resumes, including skills, qualifications, and relevant experience. This information is then used to assess the suitability of candidates for specific job roles. NLP, in combination with language models, plays a pivotal role in the automation of the resume analysis process, providing faster, more accurate results.

How Langchain Enhances NLP?

Langchain, a robust language processing tool, enhances NLP capabilities by offering a comprehensive suite of text analysis and information extraction tools. It takes advantage of language models to provide advanced natural language understanding, text splitting, embeddings, sequential searches, and question-answering capabilities. Here’s how Langchain enhances NLP for resume ranking:

  • Text Splitting: Langchain allows for efficient text splitting, breaking down lengthy documents into manageable chunks. This is particularly useful when processing lengthy resumes, ensuring better efficiency and accuracy.
  • Embeddings: Langchain facilitates the creation of embeddings, which are numerical representations of text. These embeddings help in comparing and matching keywords and phrases, a crucial component of resume ranking.
  • Sequential Search: Langchain supports sequential searches, which enable the system to locate specific information within resumes. This includes extracting details like the applicant’s name, contact information, and any relevant remarks.

Question-Answer Retrieval: Langchain’s question-answering capabilities streamline the extraction of pertinent data from resumes. This feature automates the process of understanding and ranking candidates based on keyword matches and distinct keyword types.

Langchain’s seamless integration of language models and NLP techniques contributes to the automation of the resume ranking process, making it faster, more accurate, and tailored to specific job requirements. It exemplifies the synergy between cutting-edge language models and NLP, offering a strategic advantage in the competitive landscape of hiring.

Creating the Foundation

Building a Flask Web Application

Flask, a Python web framework, serves as the foundation for our resume ranking application. It enables us to create a user-friendly interface for users to interact with the app. Flask’s simplicity and flexibility make it an ideal choice for building web applications.

Designing the User Interface

The user interface of our app will feature a keyword selection box and a JobID selection dropdown. These elements will allow users to specify the key skills they are looking for and the job positions (JobIDs) they are interested in. The combination of HTML, CSS, and JavaScript will be employed to design an intuitive and visually appealing interface.

resume ranking with langchain | resume ranking dashboard

Retrieving Resume Data

Connecting to Amazon S3

Our application assumes that candidate resumes are stored in an Amazon S3 bucket, organized by their respective JobIDs. To access and retrieve these resumes, we establish a connection to Amazon S3 using the AWS SDK for Python (Boto3).

Fetching Folders and Files

Once users select their desired keywords and JobIDs, the application must fetch the corresponding resumes from the S3 bucket. This involves listing objects in the bucket and extracting folder names associated with JobIDs.

The code for fetching folders is as follows:

def get_folders():
        # List objects in the S3 bucket and extract folder names
        objects_response = s3.list_objects_v2(Bucket=bucket_name, Delimiter="/")
        folders = []

        for common_prefix in objects_response.get("CommonPrefixes", []):
            folder_name = common_prefix["Prefix"].rstrip("/")

        return jsonify(folders)
    except Exception as e:
        return jsonify({"error": str(e)}),
  • This code defines a function get_folders to fetch folder names from an S3 bucket.
  • It lists objects in the bucket and extracts folder names using the list_objects_v2 method.
  • The extracted folder names are stored in the folders list and returned as JSON.

Extracting Resume Content

To analyze the content of resumes, we need to extract text from PDF files. For this purpose, we utilize AWS Textract, a service that converts PDF content into machine-readable text. Here’s how we extract content from PDFs:

if pdf_content == []:
            # Use Textract to extract text from the PDF
            textract_response = textract.start_document_text_detection(
                DocumentLocation={"S3Object": {"Bucket": bucket_name, "Name": pdf_file}}
            # Get the JobId from the Textract response
            textract_job_id = textract_response["JobId"]

            # Wait for the Textract job to complete
            while True:
                textract_job_response = textract.get_document_text_detection(
                textract_job_status = textract_job_response["JobStatus"]
                if textract_job_status in ["SUCCEEDED", "FAILED"]:

            if textract_job_status == "SUCCEEDED":
                # Retrieve the extracted text from the Textract response
                textract_blocks = textract_job_response["Blocks"]
                extracted_text = ""
                pdf_content = []

                for block in textract_blocks:
                    if block["BlockType"] == "LINE":
                        extracted_text += block["Text"] + "\n"
  • This code uses AWS Textract to extract text content from PDF files.
  • It initiates text detection using Textract and waits for the job to complete.
  • If the Textract job succeeds, it extracts the text from the response and appends it to the pdf_content list.

Harnessing the Power of Langchain

Text Processing with Langchain

With resume content in hand, we can now tap into the capabilities of Langchain. One crucial step is text splitting, where we divide the text into manageable chunks. This is especially helpful for processing large documents efficiently.

Here’s how we achieve text splitting with Langchain:

text_splitter = CharacterTextSplitter(chunk_size=1000, chunk_overlap=0)
                texts = text_splitter.create_documents(pdf_content)
                embeddings = OpenAIEmbeddings()
                docsearch = FAISS.from_documents(texts, embeddings)
                qa = RetrievalQA.from_chain_type(
  • Text Splitting: The code initializes a text_splitter using CharacterTextSplitter. It breaks down the text content from PDF files into smaller chunks, each with a maximum size of 1000 characters. This step helps manage and process large documents efficiently.
  • Embeddings and Document Search: After splitting the text, the code creates embeddings, which are numerical representations of text, using OpenAIEmbeddings. Then, it constructs a document search system (docsearch) using FAISS, allowing for efficient similarity-based searches among the text chunks.
  • Question-Answer Retrieval Setup: The code configures a Question-Answer (QA) retrieval system (qa) using Langchain. It specifies the Language Model (llm) as OpenAI, defines the retrieval type as “stuff,” and sets the retriever to use the docsearch created earlier. Additionally, it suppresses verbose output (verbose=False) during the QA retrieval process. This setup prepares the system to extract specific information from the text chunks efficiently.

Sequential Search and Question-Answer Retrieval

Langchain’s capabilities extend to sequential search and question-and-answer retrieval. These features allow us to extract specific information from resumes automatically. For example, we can use sequential search to locate the applicant’s name, phone number, email address, and any relevant remarks.

Here’s a glimpse of how we implement this:

name ="Name of Applicant is ")
remarks ="Does Applicant mention about any keywords from '{keywords}' ")
 answer ="Does it contain {keyword} ?")
 # Join the list of strings into a single string
pdf_content_text = "\n".join(pdf_content)
# Create a dictionary to store the data for this PDF file
pdf_content_data = {}
pdf_content_data["name"] = name
pdf_content_data["filename"] = pdf_file
pdf_content_data["remarks"] = remarks
  • Information Extraction: The code uses Langchain’s QA retrieval to extract crucial information from a resume. It searches for the applicant’s name and checks if specific keywords are mentioned in the document.
  • Text Consolidation: It joins the extracted text from the PDF resume into a single string for easier handling and analysis.
  • Data Organization: The extracted information, including the name, filename, and remarks about keyword mentions, is organized into a dictionary named pdf_content_data for further processing and presentation.

Analyzing and Ranking Resumes

Counting Keyword Occurrences

To rank resumes effectively, we need to quantify the relevance of each resume to the specified keywords. Counting the occurrences of keywords within each resume is essential for this purpose. We iterate through the keywords and tally their occurrences in each resume:

for keyword in keywords:
                keyword_count = pdf_content_text.lower().count(keyword)
                pdf_content_data[f"{keyword}"] = keyword_count

Implementing a Ranking Algorithm

The ranking of resumes is a critical aspect of our application. We prioritize resumes based on two factors: the number of distinct keyword types found and the sum of keyword counts. A ranking algorithm ensures that resumes with a higher keyword match score are ranked more prominently:

def rank_sort(pdf_content_data, keywords):
    # Priority 1: Number of keyword types found
    num_keywords_found = sum(
        1 for keyword in keywords if pdf_content_data[keyword] > 0
    # Priority 2: Sum of keyword counts
    keyword_count_sum = sum(
        int(pdf_content_data[keyword]) for keyword in keywords_list
    return (-num_keywords_found, -keyword_count_sum)
  • Priority-Based Ranking: The function ranks resumes by considering two priorities – the number of unique keywords found in the resume and the total count of keyword occurrences.
  • Keyword Matching: It assesses resumes based on how many unique keywords (from a given list) are found within them. Resumes with more matching keywords receive higher rankings.
  • Counting Keyword Occurrences: In addition to uniqueness, the function considers the total count of keyword occurrences in a resume. Resumes with higher keyword counts are ranked more favorably, helping to identify the most relevant candidates.

Displaying Result

Designing the Result Page with JavaScript

A well-designed result page is essential for presenting the ranked resumes to users. We use JavaScript to create an interactive and dynamic result page that showcases applicant names, remarks, rankings, and the number of keyword occurrences. Here’s a simplified example:

resume ranking with langchain | displaying the result

Presenting applicant Information

The result page not only displays rankings but also provides valuable information about each applicant. Users can quickly identify the most suitable candidates based on their qualifications and keyword matches.

Fine Tuning and Customization

Adapting to Different File Formats

While we’ve primarily focused on processing PDF files, our application can be adapted to handle various file formats, such as DOCX. This flexibility ensures that resumes in different formats can be analyzed effectively.

Customizing Keywords and Ranking Criteria

Customization is a key feature of our application. Users can define their own set of keywords and ranking criteria based on the specific qualifications they seek in job applicants. This adaptability makes the application suitable for a wide range of recruitment scenarios.

Deployment and Scaling

Preparing for Deployment

Before deploying the application, it’s crucial to ensure that it operates seamlessly in a production environment. This includes setting up the necessary infrastructure, configuring security measures, and optimizing performance.

Scaling for Large Scale Resume Processing

As the volume of resumes increases, our application should be designed to scale horizontally. Cloud-based solutions, such as AWS Lambda, can be employed to handle large-scale resume processing efficiently.

Security Considerations

Safeguarding Sensitive Information

Resumes often contain sensitive personal information. Our application must implement robust security measures to protect this data. This includes encryption, access controls, and compliance with data protection regulations.

Secure AWS S3 Access

Ensuring secure access to the AWS S3 bucket is paramount. Properly configuring AWS IAM (Identity and Access Management) roles and policies is essential to prevent unauthorized access.

Real-World Implementations

Companies and Organizations Utilizing AI-Powered Resume Ranker

Many companies and organizations like Glassdoor, indeed, your parking space, etc. have embraced the Langchain-Powered Resume Ranker to simplify their hiring processes. This advanced tool helps them quickly find the most suitable job candidates by automatically analyzing and ranking resumes. It’s like having a smart assistant that can go through heaps of resumes in just a few seconds, making the hiring process faster and more efficient.

User Experiences and Feedback

Users who have employed the Langchain-Powered Resume Ranker have shared their experiences and feedback. They appreciate how it works quickly and smartly to identify the resumes that perfectly match their job requirements. This means they can make better decisions when hiring new team members, and they can do it faster. The tool takes away the stress of sifting through numerous resumes and makes the hiring process smoother and more enjoyable for everyone involved.

Scalability and Adaptability to Different Industries

The Langchain-Powered Resume Ranker is adaptable to various industries. Whether it’s healthcare, technology, finance, or any other sector, customize this tool to fit the unique needs of different industries. Moreover, it can handle different file formats, like PDFs or DOCX, which makes it suitable for a wide range of job openings. So, don’t limit to one specific field; it’s a versatile solution for many different industries.

In the real world, companies are finding this tool to be a time-saving and efficient way to find the best candidates for their job openings, and it’s proving its adaptability across various industries.


In this guide, we’ve explored the creation of a resume-ranking application powered by Langchain, streamlining candidate selection with advanced technology. By integrating Langchain’s language processing capabilities and smart ranking algorithms, we’ve transformed the time-consuming process of sorting through resumes into an efficient and effective system. This tool not only accelerates the hiring process but also ensures precision in identifying the best candidates.

Key Takeaways

  • Efficiency in Hiring: The Langchain-Powered Resume Ranker offers a time-saving solution for organizations by swiftly and accurately filtering and ranking resumes based on key skills.
  • Advanced Technology: Leveraging Langchain’s capabilities, the application provides cutting-edge text analysis and information extraction.
  • Customization and Scalability: Adapt the tool to fit various job requirements and scaled for large-scale resume processing.
  • Strategic Advantage: In the competitive job market, this technology offers a strategic edge by improving efficiency and accuracy in candidate evaluation.

By adopting this automation and innovation, organizations can enhance their talent acquisition processes while maintaining flexibility and security, ensuring they stay at the forefront of the evolving hiring landscape.

Frequently Asked Questions

Q1. What is Langchain, and why is it beneficial for resume ranking?

A. Langchain is a comprehensive language processing tool that enables automatic text analysis and information extraction. Its benefits include efficiency, accuracy, and the ability to extract specific details from resumes.

Q2. How does the app rank resumes?

A. Resumes are ranked based on a scoring system that considers the number of distinct keyword types found and the sum of keyword counts. Resumes with higher scores receive higher rankings.

Q3. Can this app handle different file formats?

A. Yes, while our primary focus is on PDF files, you can extend the app to handle various file formats, including DOCX, to accommodate different resume formats.

Q4. Can I customize the keywords used for ranking?

A. Absolutely! Users can define their own set of keywords and ranking criteria to match their specific job requirements.

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Pauline I C 20 Oct 2023

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