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Back 🐍 What is NLTK (Natural Language Toolkit)? 12 Apr, 2025

NLTK (Natural Language Toolkit) is a powerful Python library for working with human language data. It provides easy-to-use interfaces to over 50 corpora and lexical resources like WordNet, along with a suite of text processing libraries for:

  • Tokenization

  • Text classification

  • Stemming and Lemmatization

  • POS tagging

  • Parsing and Syntax Tree generation

  • NER (Named Entity Recognition)

  • Language modeling

  • Semantic reasoning


📦 Key Features of NLTK

Feature Description
nltk.tokenize Break text into words/sentences
nltk.corpus Access large text collections like Gutenberg, Reuters
nltk.stem Includes stemmers like Porter, Lancaster
nltk.pos_tag() Tags parts of speech (e.g., noun, verb)
nltk.ne_chunk() Identifies named entities
nltk.FreqDist() Frequency distribution of words
nltk.sentiment Built-in sentiment analysis tools

⚙️ Example Code Snippet using NLTK

import nltk
from nltk.tokenize import word_tokenize
from nltk.corpus import stopwords
from nltk.stem import PorterStemmer

# Download required data
nltk.download('punkt')
nltk.download('stopwords')

# Sample text
text = "Natural Language Processing is an exciting field of Artificial Intelligence."

# Tokenization
tokens = word_tokenize(text)

# Stopword removal
stop_words = set(stopwords.words('english'))
filtered = [word for word in tokens if word.lower() not in stop_words]

# Stemming
stemmer = PorterStemmer()
stemmed = [stemmer.stem(word) for word in filtered]

print("Original:", tokens)
print("Filtered:", filtered)
print("Stemmed:", stemmed)

📚 When to Use NLTK?

  • When you want control and transparency in NLP tasks

  • For educational purposes

  • For quick prototyping with classical NLP

For production-level or large-scale NLP, consider using spaCy or transformers which are more optimized.