+- The Lumin Archive (https://theluminarchive.co.uk)
+-- Forum: The Lumin Archive — Core Forums (https://theluminarchive.co.uk/forumdisplay.php?fid=3)
+--- Forum: Courses — Structured Learning (https://theluminarchive.co.uk/forumdisplay.php?fid=69)
+---- Forum: Beginner’s Guide to Coding — Python From Zero to Skill (https://theluminarchive.co.uk/forumdisplay.php?fid=72)
+---- Thread: CHAPTER 16 — File Handling: Reading & Writing Data (/showthread.php?tid=234)
CHAPTER 16 — File Handling: Reading & Writing Data - Leejohnston - 11-15-2025
Chapter 16 — File Handling: Reading & Writing Data
This chapter teaches how Python reads and saves real files — unlocking data storage, logs, documents, and real applications.
Programs become powerful when they interact with files:
• save notes
• keep scores
• store settings
• load data
• create logs
• write reports
Python makes this simple using the built-in open() function.
---
16.1 Opening a File
Format:
Code:
open(filename, mode)Common modes:
Code:
"r" read only
"w" write (overwrites file)
"a" append (add to end)
"r+" read & write---
16.2 Reading a File
Example file: notes.txt
Code:
with open("notes.txt", "r") as file:
content = file.read()
print(content)with automatically closes the file — very important.
---
16.3 Reading Line by Line
Code:
with open("data.txt", "r") as file:
for line in file:
print(line.strip()).strip() removes the newline at the end.
---
16.4 Writing to a File
"w" overwrites the file:
Code:
with open("output.txt", "w") as file:
file.write("Hello from Python!\n")If the file doesn't exist, Python creates it.
---
16.5 Appending to a File
"a" adds content without deleting what's already inside.
Code:
with open("log.txt", "a") as file:
file.write("New entry added.\n")---
16.6 Writing Multiple Lines
Code:
lines = ["First line\n", "Second line\n", "Third line\n"]
with open("multi.txt", "w") as f:
f.writelines(lines)---
16.7 Checking if a File Exists
Code:
import os
if os.path.exists("test.txt"):
print("File found!")
else:
print("Not found.")---
16.8 Reading Data and Converting Types
Example file:
5
12
27
Reading as numbers:
Code:
numbers = []
with open("nums.txt", "r") as f:
for line in f:
numbers.append(int(line))
print(numbers)---
16.9 Saving Structured Data (Simple Format)
Saving:
Code:
with open("profile.txt", "w") as f:
f.write("name=Mia\n")
f.write("age=14\n")Reading:
Code:
profile = {}
with open("profile.txt", "r") as f:
for line in f:
key, value = line.strip().split("=")
profile[key] = valueNow:
Code:
profile["name"]
profile["age"]---
16.10 Using JSON for Data Storage
Perfect for storing dictionaries.
Code:
import json
data = {"name": "Lee", "score": 95}
with open("save.json", "w") as f:
json.dump(data, f)Loading:
Code:
with open("save.json", "r") as f:
loaded = json.load(f)
print(loaded)---
16.11 Mini Project — Simple Notes App
Write a program:
1. Ask the user to type a note
2. Append it to notes.txt
3. Confirm “Note saved.”
Each new note goes on a new line.
---
16.12 Challenge — High Score System
Requirements:
• File: highscores.txt
• Ask for a player name and score
• Save them in the format:
Code:
Mia: 42• After saving, load the whole file
• Display all scores sorted by score
BONUS:
Find the highest scorer and display their name.
---
16.13 Chapter Summary
• open() controls reading/writing
• "w" overwrites, "a" appends
• use with open(...) to avoid errors
• .read(), .readline(), loops for reading
• JSON is excellent for structured data
• file handling allows real persistent programs
Next:
Chapter 17 — Errors & Exception Handling
This is where beginners learn how to make programs crash-proof, safe, and professional.
---
Written and Compiled by Lee Johnston — Founder of The Lumin Archive