For detailed explanation, please refer to my blog post : http://www.filipyoo.com/topic-and-sentiment-analysis-using-twitter-api/

Classify tweets by sentiment for a specific given product

Airline sentiment using Naive-Bayes Classification of airline tweets

Analyze your twitter sentiments by tweet and tags

Heavy Heart uses data collected on random users publicly posted tweets to diagnose users with early stages of depression.

This script performs sentiment analysis of any topic by parsing the tweets fetched from Twitter using Python.