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

class ClassName:
    # Class attributes and methods

class Dog:
    # Class attributes (shared by all instances)
    species = "Canis familiaris"
    
    # Constructor method to initialize instance attributes
    def __init__(self, name, age):
        self.name = name  # Instance attribute
        self.age = age    # Instance attribute
    
    # Method to display dog's information
    def display_info(self):
        print(f"My dog {self.name} is {self.age} years old.")

dog1 = Dog("Buddy", 4)  # Creating an object of the Dog class
dog1.display_info()      # Output: My dog Buddy is 4 years old.

class Car:
    # Class variable (shared by all instances)
    wheels = 4
    
    def __init__(self, model, color):
        # Instance variables (unique to each instance)
        self.model = model
        self.color = color

car1 = Car("Toyota", "Red")
car2 = Car("Honda", "Blue")

print(car1.wheels)  # Output: 4
print(car2.wheels)  # Output: 4
print(car1.model)   # Output: Toyota
print(car2.color)   # Output: Blue

class Rectangle:
    def __init__(self, width, height):
        self.width = width
        self.height = height
    
    # Method to calculate area
    def area(self):
        return self.width * self.height

rect1 = Rectangle(10, 5)
print(f"Area of rectangle: {rect1.area()}")  # Output: Area of rectangle: 50

class Circle:
    def __init__(self, radius):
        self.radius = radius
    
    def circumference(self):
        return 2 * 3.1416 * self.radius

circle1 = Circle(7)
print(f"Circumference of circle: {circle1.circumference()}")  # Output: 43.9824

class Student:
    def __init__(self, name, grade):
        self.name = name
        self.grade = grade
    
    def update_grade(self, new_grade):
        self.grade = new_grade

student1 = Student("Alice", "A")
student1.update_grade("B")
print(f"{student1.name} has a grade of {student1.grade}.")  # Output: Alice has a grade of B.

class ParentClass:
    # Parent class code

class ChildClass(ParentClass):
    # Child class code (inherits from ParentClass)

class Animal:
    def __init__(self, name):
        self.name = name
    
    def speak(self):
        print(f"{self.name} makes a sound.")

class Dog(Animal):  # Dog inherits from Animal
    def speak(self):
        print(f"{self.name} barks.")

dog1 = Dog("Buddy")
dog1.speak()  # Output: Buddy barks.