Your programs have been losing all data when they close
Type something, run the program, close it — gone forever
File handling fixes that
You can now read and write data to actual files on your computer
This is how bots save user data, logs, and settings without a database
This lecture covers:
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You open a file using open() and specify a mode:
Always use the with statement — it closes the file automatically:
with open("notes.txt", "w") as file:
file.write("Hello from Python!")
# file is automatically closed after the with blockNever open files without with unless you have a specific reason
Forgetting to close files causes memory leaks in long running programs
Bots run 24/7 — this matters
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📌 Reading Files
First create a file called notes.txt and add some text manually
Then read it:
Always handle the case where the file does not exist:
First create a file called notes.txt and add some text manually
Then read it:
# read entire file as one string
with open("notes.txt", "r") as file:
content = file.read()
print(content)
# read line by line — useful for large files
with open("notes.txt", "r") as file:
for line in file:
print(line.strip()) # strip removes the newline at the end
# read all lines into a list
with open("notes.txt", "r") as file:
lines = file.readlines()
print(lines[0]) # first line
Always handle the case where the file does not exist:
try:
with open("notes.txt", "r") as file:
content = file.read()
except FileNotFoundError:
print("File not found")
Writing — overwrites everything in the file:
with open("log.txt", "w") as file:
file.write("Bot started
")
file.write("Listening for messages
")Appending — adds to the end without deleting existing content:
with open("log.txt", "a") as file:
file.write("New user joined
")Writing multiple lines at once:
lines = ["line one
", "line two
", "line three
"]
with open("output.txt", "w") as file:
file.writelines(lines)
The
is a newline character — without it everything ends up on one line
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Storing data as plain text is limited
JSON lets you save structured data like dictionaries and lists to a file
This is the most common way bots store simple data
Saving data to a JSON file:
import json
users = {
"ahmed": {"age": 22, "is_banned": False},
"sara": {"age": 19, "is_banned": False}
}
with open("users.json", "w") as file:
json.dump(users, file, indent=4)
Loading data from a JSON file:
import json
with open("users.json", "r") as file:
users = json.load(file)
print(users["ahmed"]["age"]) # 22
indent=4 makes the file human readable — always use it
You will use this exact pattern for storing bot user data, settings, and configs
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Watch this after reading through all the posts
Python Full Course 2024 — freeCodeCamp
Covers file I/O, appending, with keyword, reading files, CSV files, and binary files
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Build a persistent to-do list — one that saves and loads from a file:
import json
import os
FILENAME = "todos.json"
def load_todos():
if os.path.exists(FILENAME):
with open(FILENAME, "r") as f:
return json.load(f)
return []
def save_todos(todos):
with open(FILENAME, "w") as f:
json.dump(todos, f, indent=4)
todos = load_todos()
while True:
print("
1. View todos")
print("2. Add todo")
print("3. Delete todo")
print("4. Exit")
choice = input("Choose: ")
if choice == "1":
for i, task in enumerate(todos):
print(f"{i + 1}. {task}")
elif choice == "2":
task = input("New task: ").strip()
todos.append(task)
save_todos(todos)
print("Saved!")
elif choice == "3":
num = int(input("Task number to delete: ")) - 1
removed = todos.pop(num)
save_todos(todos)
print(f"Deleted: {removed}")
elif choice == "4":
break
Run it, add tasks, close it, run it again — your tasks are still there
That is persistence
Screenshot your output
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Everything you have learned so far is procedural programming
Code that runs step by step, top to bottom
OOP is a different way of thinking about code
Instead of writing functions that do things
You create objects that have their own data and their own functions
Every major library you will use — aiogram, pyrogram, telethon — is built with OOP
You need to understand it to read and write real code
This lecture covers:
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A class is a blueprint
An object is something built from that blueprint
Think of a class as the design for a car
An object is the actual car built from that design
You can build many cars from one design — each a separate object
class Dog:
pass # empty class for now
dog1 = Dog() # create an object from the class
dog2 = Dog() # another object — completely separate
print(type(dog1)) # <class 'main.Dog'>
dog1 and dog2 are both Dogs but they are separate objects
Changes to one do not affect the other
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init runs automatically when you create an object
It is where you set the initial data for the object
self refers to the object itself
class User:
def init(self, name, age):
self.name = name
self.age = age
user1 = User("Ahmed", 22)
user2 = User("Sara", 19)
print(user1.name) # Ahmed
print(user2.age) # 19
self.name and self.age are attributes — data that belongs to each object
user1 has its own name and age, user2 has its own
They do not share data
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Methods are functions that belong to a class
They always take self as the first parameter
class User:
def init(self, name, age):
self.name = name
self.age = age
self.is_banned = False
def greet(self):
print(f"Hello I am {self.name} and I am {self.age} years old")
def ban(self):
self.is_banned = True
print(f"{self.name} has been banned")
def status(self):
if self.is_banned:
print(f"{self.name}: Banned")
else:
print(f"{self.name}: Active")
user1 = User("Ahmed", 22)
user1.greet()
user1.ban()
user1.status()
Output:
Hello I am Ahmed and I am 22 years old
Ahmed has been banned
Ahmed: Banned
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A class can inherit from another class
It gets all the parent's attributes and methods for free
Then you add or override what you need
class User:
def init(self, name):
self.name = name
def greet(self):
print(f"Hello I am {self.name}")
class Admin(User): # Admin inherits from User
def init(self, name):
super().init(name) # call parent init
self.permissions = ["ban", "mute", "delete"]
def show_permissions(self):
print(f"{self.name} can: {', '.join(self.permissions)}")
admin = Admin("Ahmed")
admin.greet() # inherited from User
admin.show_permissions() # Admin's own method
super() calls the parent class
You will see this everywhere in aiogram and pyrogram code
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When you write a Telegram bot you will see things like this:
from aiogram import Bot, Dispatcher
from aiogram.types import Message
bot = Bot(token="YOUR_TOKEN") # creating an object from the Bot class
dp = Dispatcher() # creating an object from the Dispatcher class
@dp.message()
async def handle(message: Message): # Message is a class
print(message.text) # attribute
print(message.from_user.first_name) # nested object attribute
await message.reply("Hello!") # calling a method on the object
Bot, Dispatcher, Message — all classes
bot, dp, message — all objects
message.text, message.from_user — attributes
message.reply() — a method
Now when you see this in the next lecture it will make complete sense
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Watch this after reading through all the posts
Python Full Course 2024 — freeCodeCamp
Covers OOP, classes, attributes, methods, inheritance, operator overloading, and class methods
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Build a simple user management system using OOP:
class User:
def init(self, name, age):
self.name = name
self.age = age
self.is_banned = False
self.messages = []
def send_message(self, text):
if self.is_banned:
print(f"{self.name} is banned and cannot send messages")
return
self.messages.append(text)
print(f"{self.name}: {text}")
def ban(self):
self.is_banned = True
print(f"{self.name} has been banned")
def unban(self):
self.is_banned = False
print(f"{self.name} has been unbanned")
def show_history(self):
print(f"
{self.name} message history:")
for msg in self.messages:
print(f" - {msg}")
user1 = User("Ahmed", 22)
user2 = User("Sara", 19)
user1.send_message("Hello everyone!")
user2.send_message("Hey!")
user1.ban()
user1.send_message("Can you hear me?")
user1.unban()
user1.send_message("I am back!")
user1.show_history()
Run it and screenshot the output
Bonus — create an Admin class that inherits from User and has a ban() method that can ban other users
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