Sentiment analysis, also known as opinion mining, is a natural language processing (NLP) technique used to determine the emotional tone behind a body of text. It's widely used to analyze customer feedback, social media comments, and reviews. This blog will guide you through the process of performing sentiment analysis in Python, leveraging powerful libraries such as NLTK, TextBlob, and VADER.

Prerequisites

Before we begin, ensure you have Python installed on your system. You’ll also need to install some libraries. Open your terminal and run the following commands:

pip install nltk
pip install textblob
pip install vaderSentiment

Step 1: Import Necessary Libraries

First, we need to import the libraries we’ll be using:

import nltk
from nltk.sentiment.vader import SentimentIntensityAnalyzer
from textblob import TextBlob

Step 2: Download NLTK Data

For NLTK, we need to download the VADER lexicon, a pre-trained sentiment analysis model:

nltk.download('vader_lexicon')

Step 3: Sentiment Analysis with VADER

VADER (Valence Aware Dictionary and sEntiment Reasoner) is specifically attuned to sentiments expressed in social media. It uses a combination of a lexicon and a set of rules to perform sentiment analysis.

def vader_sentiment(text):
    sia = SentimentIntensityAnalyzer()
    sentiment = sia.polarity_scores(text)
    return sentiment

text = "I love Python. It's such a powerful language!"
print(vader_sentiment(text))

The output will be a dictionary with the keys neg, neu, pos, and compound:

{'neg': 0.0, 'neu': 0.292, 'pos': 0.708, 'compound': 0.6696}

• neg: Negative sentiment score

• neu: Neutral sentiment score

• pos: Positive sentiment score

• compound: Overall sentiment score, ranging from -1 (most negative) to +1 (most positive)

Step 4: Sentiment Analysis with TextBlob

TextBlob is another powerful library for processing textual data. It provides a simple API for diving into common NLP tasks, including sentiment analysis.

def textblob_sentiment(text):
    blob = TextBlob(text)
    sentiment = blob.sentiment
    return sentiment

text = "I love Python. It's such a powerful language!"
print(textblob_sentiment(text))

The output will be a named tuple with polarity and subjectivity:

Sentiment(polarity=0.5, subjectivity=0.6)

• polarity: Ranges from -1 (negative) to +1 (positive)

• subjectivity: Ranges from 0 (objective) to 1 (subjective)

Step 5: Analyzing a Dataset

Let's analyze a dataset of movie reviews to see sentiment analysis in action. We'll use the pandas library to handle our data.

import pandas as pd

# Sample data
data = {
    'review': [
        "I loved the movie. It was fantastic!",
        "I hated the film. It was awful.",
        "The movie was okay, not great but not bad either.",
        "What a waste of time. Terrible acting!",
        "An absolute masterpiece. Brilliant performance!"
    ]
}

df = pd.DataFrame(data)

Adding Sentiment Scores to the DataFrame

We'll use both VADER and TextBlob to add sentiment scores to our DataFrame.

def add_vader_sentiment(df):
    sia = SentimentIntensityAnalyzer()
    df['vader_sentiment'] = df['review'].apply(lambda x: sia.polarity_scores(x)['compound'])
    return df

def add_textblob_sentiment(df):
    df['textblob_sentiment'] = df['review'].apply(lambda x: TextBlob(x).sentiment.polarity)
    return df

df = add_vader_sentiment(df)
df = add_textblob_sentiment(df)
print(df)

The DataFrame now includes sentiment scores from both VADER and TextBlob:

Step 6: Visualizing Sentiment

Finally, let's visualize the sentiment distribution using matplotlib.

import matplotlib.pyplot as plt

plt.figure(figsize=(10, 5))

# VADER sentiment
plt.subplot(1, 2, 1)
plt.hist(df['vader_sentiment'], bins=10, color='blue', alpha=0.7)
plt.title('VADER Sentiment Distribution')
plt.xlabel('Sentiment Score')
plt.ylabel('Frequency')

# TextBlob sentiment
plt.subplot(1, 2, 2)
plt.hist(df['textblob_sentiment'], bins=10, color='green', alpha=0.7)
plt.title('TextBlob Sentiment Distribution')
plt.xlabel('Sentiment Score')
plt.ylabel('Frequency')

plt.tight_layout()
plt.show()

Happy coding!