def check_age(age):
    if age < 18:
        raise ValueError("Age must be 18 or above.")
    return "Valid age"

try:
    check_age(16)
except ValueError as e:
    print(e)

class InvalidAgeError(Exception):
    """Custom exception for invalid age."""
    pass

def check_age(age):
    if age < 18:
        raise InvalidAgeError("You must be at least 18 years old.")
    return "Valid age"

try:
    check_age(16)
except InvalidAgeError as e:
    print(e)

try:
    raise ValueError("An error occurred")
except Exception as e:
    print("Caught an exception:", e)

assert condition, message

age = 15
assert age >= 18, "Age must be 18 or above!"

Write a Python program that implements a calculator with functions for addition, subtraction, multiplication, and division. Use exception handling to catch invalid inputs and division by zero.

Welcome to Day 12 of the "Noob to Pro in Python" course! Today, we will learn about modules and packages in Python. Understanding how to organize your code into modules and packages is crucial for creating maintainable, reusable, and scalable programs. We will also explore Python’s built-in modules and learn how to create your own.

A module is simply a Python file (with a .py extension) that contains Python code. It may contain functions, classes, variables, and runnable code. Instead of writing all your code in a single file, you can split it into multiple files (modules) and use them in different parts of your project.

# This is a simple module with a function

def greet(name):
    return f"Hello, {name}!"

import mymodule

print(mymodule.greet("Alice"))  # Output: Hello, Alice!

import mymodule

from mymodule import greet

import mymodule as mm

print(mm.greet("Bob"))  # Output: Hello, Bob!

from mymodule import *

Python comes with a wide range of built-in modules that provide functionality for common tasks. Some popular built-in modules include:

import math

print(math.sqrt(16))    # Output: 4.0
print(math.pi)          # Output: 3.141592653589793

import random

print(random.randint(1, 10))  # Output: Random integer between 1 and 10

import datetime

now = datetime.datetime.now()
print(now)  # Output: Current date and time

mypackage/
    __init__.py
    module1.py
    module2.py

# This is the initialization file for the package

def add(a, b):
    return a + b

def subtract(a, b):
    return a - b

from mypackage import module1, module2

print(module1.add(10, 5))      # Output: 15
print(module2.subtract(10, 5)) # Output: 5

pip install package_name

pip install requests

import requests

response = requests.get("https://jsonplaceholder.typicode.com/posts/1")
print(response.json())

pip install package_name

python -m venv myenv

# Windows
myenv\Scripts\activate

# Mac/Linux
source myenv/bin/activate

pip install package_name

pip freeze > requirements.txt

pip install -r requirements.txt