Data Loading and Text Chunking Basics
Learn how to load unstructured data and apply effective text chunking strategies for optimal retrieval performance.
Data Loading and Text Chunking Basics is a free LLM Apps in Production (RAG + Vector DB + Caching) lesson on CoddyKit — lesson 2 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the LLM Apps in Production (RAG + Vector DB + Caching) learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Loading Data for RAG
Welcome to Lesson 2! In Retrieval Augmented Generation (RAG), the first step is always to get your data ready. This means loading your information and preparing it for the Large Language Model (LLM).
Most real-world data is unstructured, meaning it doesn't fit neatly into rows and columns like a spreadsheet. Think of documents, web pages, or books.
Common Unstructured Data Sources
RAG systems can work with many types of unstructured data. Here are some common examples:
- Text files (.txt): Simple, plain text documents.
- PDFs (.pdf): Often contain text, images, and complex layouts.
- Word Documents (.docx): Rich text with formatting.
- Web Pages (.html): Content from websites.
- Databases/APIs: Text extracted from various fields.
The goal is to extract the raw text content from these sources.
Basic Text File Loading
Let's start with the simplest form: loading a plain text file. In Python, you can easily read the entire content of a file into a string.
This example creates a small sample.txt and then reads its content.
import os
def load_text_file(filepath):
with open(filepath, 'r', encoding='utf-8') as f:
return f.read()
if __name__ == "__main__":
# Create a dummy file for demonstration
file_content = "This is the first line.\nThis is the second line.\nAnd a final line of text."
with open("sample.txt", "w", encoding="utf-8") as f:
f.write(file_content)
# Load and print the content
loaded_data = load_text_file("sample.txt")
print("--- Loaded Content ---")
print(loaded_data)
# Clean up the dummy file
os.remove("sample.txt")Why Text Chunking is Essential
Once you've loaded your data, you can't usually send an entire book or long document directly to an LLM. Why not?
- Context Window Limits: LLMs have a maximum amount of text they can process at once.
- Cost: Sending very long texts is expensive, as you're typically charged per token.
- Relevance: Shorter, focused pieces of text are often more relevant for retrieval.
This is where text chunking comes in.
Understanding the Context Window
The context window is like an LLM's short-term memory. It's the maximum number of tokens (words or sub-words) it can consider when generating a response.
- If your input text is too long, it gets truncated.
- The LLM only 'sees' what's in its context window.
Chunking breaks your big document into smaller, manageable pieces that fit within this window.
Basic Chunking: Fixed Size
The simplest chunking strategy is fixed-size chunking. You define a specific number of characters or tokens, and then split your document into chunks of that exact size.
For example, if you have a 1000-character document and a chunk size of 100, you'll get 10 chunks.
- Pros: Easy to implement.
- Cons: Can cut sentences or paragraphs in half, losing context.
Fixed-Size Chunking in Action
Here's a Python example demonstrating fixed-size chunking. Notice how the text is simply cut at regular intervals, which might sometimes break words or sentences.
def fixed_size_chunker(text, chunk_size):
chunks = []
for i in range(0, len(text), chunk_size):
chunks.append(text[i : i + chunk_size])
return chunks
if __name__ == "__main__":
sample_text = "Large language models are powerful tools for text generation and understanding. However, they have limitations, especially with very long inputs due to their context window size."
chunk_size = 40
chunks = fixed_size_chunker(sample_text, chunk_size)
print(f"Original text length: {len(sample_text)}")
print(f"Chunk size: {chunk_size}")
print("--- Chunks ---")
for i, chunk in enumerate(chunks):
print(f"Chunk {i+1} ({len(chunk)} chars): '{chunk}'")Improving Context with Overlap
Fixed-size chunking can be problematic if important context is split across two chunks. To mitigate this, we use overlapping chunks.
With overlap, each new chunk starts a bit before the previous one ended. This ensures that some text appears in multiple chunks, preserving continuity.
- A common overlap size is 10-20% of the chunk size.
- It helps the LLM connect ideas even if they span chunk boundaries.
Overlapping Chunking Example
See how adding an overlap helps maintain context. The start of each new chunk includes some text from the end of the previous one.
def overlapping_chunker(text, chunk_size, overlap_size):
chunks = []
start = 0
while start < len(text):
end = start + chunk_size
chunk = text[start:end]
chunks.append(chunk)
start += chunk_size - overlap_size
if start < 0: # Handle cases where overlap > chunk_size initially
start = 0
return chunks
if __name__ == "__main__":
text_data = "The quick brown fox jumps over the lazy dog. Dogs are mammals and often friendly animals."
chunk_size = 30
overlap_size = 10
chunks = overlapping_chunker(text_data, chunk_size, overlap_size)
print(f"Original text length: {len(text_data)}")
print(f"Chunk size: {chunk_size}, Overlap size: {overlap_size}")
print("--- Overlapping Chunks ---")
for i, chunk in enumerate(chunks):
print(f"Chunk {i+1} ({len(chunk)} chars): '{chunk}'")Check Your Understanding
You've learned about loading data and basic chunking strategies. Now, let's test your knowledge!
Recap: Data Loading & Chunking
Great job! In this lesson, we covered the foundational steps of preparing data for RAG applications:
- Data Loading: Extracting raw text from various unstructured sources like text files, PDFs, and web pages.
- Text Chunking: The essential process of breaking down long documents into smaller, manageable pieces.
- Context Window: Understanding the LLM's limitation on input text length (measured in tokens).
- Chunking Strategies: Explored basic fixed-size chunking and the improved method of fixed-size chunking with overlap to preserve context.
Next, we'll see how these chunks are used to build a simple RAG pipeline!
Frequently asked questions
Is the “Data Loading and Text Chunking Basics” lesson free?
Yes — the full text of “Data Loading and Text Chunking Basics” is free to read here on the web, and the LLM Apps in Production (RAG + Vector DB + Caching) course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the LLM Apps in Production (RAG + Vector DB + Caching) course, upgrade to CoddyKit PRO.
What will I learn in “Data Loading and Text Chunking Basics”?
Learn how to load unstructured data and apply effective text chunking strategies for optimal retrieval performance. You practise LLM Apps in Production (RAG + Vector DB + Caching) with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start LLM Apps in Production (RAG + Vector DB + Caching)?
No prior experience is required. LLM Apps in Production (RAG + Vector DB + Caching) on CoddyKit is structured for beginners through advanced learners; this is — lesson 2 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Data Loading and Text Chunking Basics” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this LLM Apps in Production (RAG + Vector DB + Caching) lesson?
Yes. Every LLM Apps in Production (RAG + Vector DB + Caching) lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Choosing an LLM Provider
- Data Loading and Text Chunking Basics
- Building a Simple RAG Pipeline
- Testing & Evaluating Your RAG App