Building Advanced Text Classification Models with Langchain in Python

In this tutorial, we will explore how to build advanced text classification models using Langchain in Python. Langchain is a powerful yet simple-to-use library that allows you to create state-of-the-art text classification models for various natural language processing (NLP) tasks, such as sentiment analysis, topic modeling, and spam detection.

Table of Contents


Before diving into the tutorial, make sure you have the following:

  • Python 3.6 or later
  • Familiarity with Python programming and basic NLP concepts


To get started, you need to install Langchain. You can install it using pip:

pip install langchain

Preparing the Data

For this tutorial, we will use the 20 Newsgroups dataset. It is a collection of approximately 20,000 newsgroup documents, partitioned across 20 different newsgroups. You can load the dataset using the following code:

from sklearn.datasets import fetch_20newsgroups

newsgroups_train = fetch_20newsgroups(subset="train", remove=("headers", "footers", "quotes"))
newsgroups_test = fetch_20newsgroups(subset="test", remove=("headers", "footers", "quotes"))

X_train =
y_train =
X_test =
y_test =

Building a Text Classification Model

With Langchain, building a text classification model is straightforward. Here's a simple example:

from langchain import TextClassifier

model = TextClassifier()

# Train the model, y_train)

# Make predictions on the test set
y_pred = model.predict(X_test)

Evaluating the Model

To evaluate the performance of your model, you can use various evaluation metrics like accuracy, precision, recall, and F1-score. Here's how you can compute these metrics:

from sklearn.metrics import accuracy_score, precision_score, recall_score, f1_score

accuracy = accuracy_score(y_test, y_pred)
precision = precision_score(y_test, y_pred, average="weighted")
recall = recall_score(y_test, y_pred, average="weighted")
f1 = f1_score(y_test, y_pred, average="weighted")

print(f"Accuracy: {accuracy:.2f}")
print(f"Precision: {precision:.2f}")
print(f"Recall: {recall:.2f}")
print(f"F1 Score: {f1:.2f}")

Improving Model Performance

To improve the performance of your text classification model, you can use various techniques, such as:

  • Text preprocessing (tokenization, stopword removal, stemming, and lemmatization)
  • Feature extraction (TF-IDF, word embeddings, and document embeddings)
  • Model tuning (hyperparameter optimization, ensemble methods, and transfer learning)

Here's an example of how to apply text preprocessing and feature extraction using Langchain:

from langchain import TextClassifier, TFIDFVectorizer, Preprocessor

preprocessor = Preprocessor(

vectorizer = TFIDFVectorizer(
    ngram_range=(1, 2),

model = TextClassifier(
), y_train)
y_pred = model.predict(X_test)


In this tutorial, you learned how to build advanced text classification models using Langchain in Python. You also learned how to evaluate and improve the performance of your models. Langchain is a powerful library that can help you create state-of-the-art NLP models with ease. Give it a try and enhance your NLP projects!

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