1. Introduction

In this tutorial, we will explore how to use popular Natural Language Processing (NLP) libraries like NLTK (Natural Language Toolkit), SpaCy, and Gensim to create a simple chatbot. We will learn how these libraries can help us process and understand human language, which is a vital part of creating a chatbot.

By the end of this tutorial, you should be able to implement basic NLP tasks such as tokenization, part-of-speech tagging, named entity recognition, and semantic similarity measurement.

Prerequisites:
- Basic Python programming
- Familiarity with the concept of chatbots

2. Step-by-Step Guide

Understanding the Libraries

• NLTK: It's a leading platform for building Python programs to work with human language data. It provides easy-to-use interfaces to over 50 corpora and lexical resources.
• SpaCy: This is an open-source software library for advanced NLP. It supports over 60 languages and has 36 statistical models.
• Gensim: It's a robust open-source NLP library. It's designed to handle large text collections using data streaming and incremental online algorithms.

3. Code Examples

Example 1: Tokenization using NLTK

# Import the required library
from nltk.tokenize import word_tokenize

# Sample text
text = "Hello, I'm your chatbot."

# Tokenize the text
tokens = word_tokenize(text)

print(tokens)

This will output: ['Hello', ',', 'I', "'m", 'your', 'chatbot', '.']

Example 2: Part-of-Speech Tagging using SpaCy

# Import the required library
import spacy

# Load the English language model
nlp = spacy.load("en_core_web_sm")

# Process a text
doc = nlp("I am a chatbot.")

# Iterate over the tokens
for token in doc:
    # Print the token and its part-of-speech tag
    print(token.text, token.pos_)

This will output: I PRON, am AUX, a DET, chatbot NOUN, . PUNCT

Example 3: Semantic Similarity Measurement using Gensim

# Import the required libraries
from gensim import corpora, similarities

# Sample texts
texts = [
    ["I", "am", "a", "chatbot"],
    ["I", "am", "a", "program"]
]

# Create a dictionary from the texts
dictionary = corpora.Dictionary(texts)

# Create a corpus from the texts
corpus = [dictionary.doc2bow(text) for text in texts]

# Create a similarity index
index = similarities.SparseMatrixSimilarity(corpus, num_features=len(dictionary))

# Print the similarity between the two texts
print(index[corpus[0]][1])

This will output a number between 0 and 1. The closer to 1, the more similar the texts are.

4. Summary

In this tutorial, we learned how to use NLTK, SpaCy, and Gensim to implement basic NLP tasks for chatbot development. We explored tokenization, part-of-speech tagging, and semantic similarity measurement.

Next steps could include learning more advanced NLP tasks, experimenting with different NLP libraries, and creating a more complex chatbot. For additional resources, check out the NLTK Book, the SpaCy documentation, and the Gensim tutorials.

5. Practice Exercises

1. Use NLTK to tokenize the following sentence: "Chatbots are becoming increasingly popular."
2. Use SpaCy to perform part-of-speech tagging on the following sentence: "Can you help me build a chatbot?"
3. Use Gensim to measure the semantic similarity between the following texts: ["I am a human"], ["I am a bot"]

Solutions:

1. ['Chatbots', 'are', 'becoming', 'increasingly', 'popular', '.']
2. Can AUX, you PRON, help VERB, me PRON, build VERB, a DET, chatbot NOUN, ? PUNCT
3. A number between 0 and 1, likely closer to 0 as the texts are not very similar.

Remember, the best way to learn is by doing. Keep practicing and experimenting!