Thursday, 30 November 2023

Classifying Text with Python: An Introduction to Natural Language Classifier in Python

08 Mar 2023

As businesses continue to generate an overwhelming amount of data, it has become increasingly important to categorize and analyze information quickly and efficiently. One way to do this is through Natural Language Classification, a process that allows you to group and label text based on its content. In this article, we will provide an introduction to Natural Language Classification in Python, and how you can use it to improve your business processes.

What is Natural Language Classification?

Natural Language Classification is the process of categorizing text into predefined groups based on the content and meaning of the text. The main goal of Natural Language Classification is to assign a label or category to a piece of text without the need for human intervention.

In practice, Natural Language Classification can be used for a wide range of applications, including sentiment analysis, spam filtering, and content tagging. For instance, it can help businesses to categorize customer feedback into positive or negative, filter out spam emails from genuine ones, and label news articles based on their content.

Introduction to Python Natural Language Classifier

Python is a popular language among data scientists and machine learning enthusiasts. It provides an extensive set of libraries for Natural Language Processing (NLP), making it an ideal choice for developing a Natural Language Classifier.

To begin with, you need to have a dataset that is labeled with predefined categories. In other words, the data should have a set of categories or labels that you want to classify the text into. For instance, if you have a dataset of customer reviews, you may want to label them as positive, negative or neutral.

Once you have your labeled dataset, you can start with the training process. The training process involves teaching the machine learning algorithm to recognize patterns and features in the text that are relevant to the labels. The more data you provide to the algorithm, the better it will become at recognizing patterns and features in the text.

To implement Natural Language Classification in Python, you can use the Natural Language Toolkit (NLTK) library. The NLTK library provides a range of tools and resources for NLP tasks, including tokenization, stemming, and lemmatization.

Steps for Implementing Natural Language Classifier in Python

Step 1: Install NLTK

The first step is to install the NLTK library in Python. You can do this by running the following command:

pip install nltk

Step 2: Import Libraries

Next, you need to import the required libraries in your Python code. Here are some of the libraries that you will need:

import nltk

import random

from nltk.corpus import movie_reviews

Step 3: Load Data

The next step is to load the labeled data that you will use for training and testing your classifier. The movie_reviews corpus in NLTK contains a set of movie reviews that are already labeled as positive or negative. You can load this data using the following code:

documents = [(list(movie_reviews.words(fileid)), category)

             for category in movie_reviews.categories()

             for fileid in movie_reviews.fileids(category)]

Step 4: Preprocess Data

The next step is to preprocess the data to prepare it for the training process. This includes tasks such as tokenization, stemming, and lemmatization. Here is an example of how to perform tokenization:

all_words = []

for w in movie_reviews.words():


all_words = nltk.FreqDist(all_words)

Step 5: Feature Extraction

The next step is to extract features from the preprocessed data. This involves selecting relevant features from the text that will be used to classify it. In this example, we will use the 2000 most frequently occurring words as features.

word_features = list(all_words.keys())[:2000]

Step 6: Split Data

The next step is to split the labeled data into training and testing sets. This is important to evaluate the performance of the classifier. In this example, we will use 80% of the data for training and 20% for testing.


training_set = documents[:1600]

testing_set = documents[1600:]

Step 7: Train and Test Classifier

The final step is to train and test the classifier. We will use the Naive Bayes algorithm for classification.

def find_features(document):

    words = set(document)

    features = {}

    for w in word_features:

        features[w] = (w in words)

    return features

featuresets = [(find_features(rev), category) for (rev, category) in documents]

training_set = featuresets[:1600]

testing_set = featuresets[1600:]

classifier = nltk.NaiveBayesClassifier.train(training_set)

print(“Accuracy:”, nltk.classify.accuracy(classifier, testing_set))

The output of the above code will give the accuracy of the classifier. You can then use this classifier to classify new text data based on the labels that it has learned from the training data.


In this article, we have provided an introduction to Natural Language Classification in Python using the Natural Language Toolkit (NLTK) library. We have covered the basic steps for implementing a Natural Language Classifier, including data preprocessing, feature extraction, and training and testing the classifier using the Naive Bayes algorithm.

Natural Language Classification is a powerful tool for categorizing and analyzing text data, and can be used for a wide range of applications. By implementing Natural Language Classification in Python, businesses can improve their processes and gain valuable insights from their data.

If you want to learn more about Natural Language Classification, we recommend exploring the NLTK library and experimenting with different algorithms and datasets. With practice, you can develop highly accurate classifiers that can help you make more informed decisions based on your text data.