Advanced Python · Week 6

Modules and Scope

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Exercise 1: Introduction to Modules

Welcome to Python 2, Lesson 6! Today, we'll learn about modules in Python. Modules are files containing Python code that can be imported and used in other Python programs.

What are Modules?

Modules are reusable pieces of code that can be imported into your Python programs. They help organize and structure your code, making it easier to maintain and reuse.

Python comes with many built-in modules that you can use right away. Let's start by importing and using the 'math' module:

import math

# Using the sqrt function from the math module
result = math.sqrt(16)
print(f"The square root of 16 is: {result}")

# Using the pi constant from the math module
circumference = 2 * math.pi * 5
print(f"The circumference of a circle with radius 5 is: {circumference:.2f}")
            

Now it's your turn! Import the 'random' module and use it to generate random numbers:

Import the 'random' module
Generate a random integer between 1 and 10 (inclusive) using random.randint()
Generate a random float between 0 and 1 using random.random()
Print both results

Starter code

# Import the random module and generate random numbers here

Write your code here

Exercise 2: Creating and Using Custom Modules

In addition to using built-in modules, you can create your own custom modules to organize your code better.

Creating Custom Modules

A module is just a Python file with a .py extension
You can import functions, classes, and variables from your custom modules
Use the 'import' keyword to use your custom modules in other Python files

Let's create a simple custom module and use it. First, we'll create a module called 'greetings.py':

# This is the content of greetings.py
def say_hello(name):
    return f"Hello, {name}!"

def say_goodbye(name):
    return f"Goodbye, {name}!"
            

Now, let's use our custom module in another Python file:

# This is a new Python file using our custom module
import greetings

print(greetings.say_hello("Alice"))
print(greetings.say_goodbye("Bob"))
            

Your turn! Create a custom module called 'calculator.py' with the following functions:

add(a, b): returns the sum of a and b
subtract(a, b): returns the difference between a and b
multiply(a, b): returns the product of a and b
divide(a, b): returns the result of a divided by b

Then, create a main program that imports your calculator module and uses all of its functions.

Starter code

# Create your calculator module and use it here

Write your code here

Exercise 3: Understanding Variable Scope

Variable scope refers to the part of a program where a variable is accessible. Understanding scope is crucial for writing clean and bug-free code.

Types of Variable Scope

Local scope: Variables defined inside a function
Global scope: Variables defined outside of any function
Enclosing scope: Variables in the outer function of nested functions
Built-in scope: Names that are pre-assigned in Python

Let's look at an example demonstrating local and global scope:

# Global variable
x = 10

def print_x():
    # Local variable
    x = 20
    print(f"Local x: {x}")

print_x()
print(f"Global x: {x}")
            

Your task:

Create a global variable called 'message' with the value "Hello, World!"
Create a function called 'change_message' that creates a local variable also called 'message' with a different value
Print both the local and global 'message' variables to see the difference

Starter code

# Demonstrate variable scope here

Write your code here

Exercise 4: Global and Local Variables

Sometimes, you might want to modify a global variable from within a function. Python provides the 'global' keyword for this purpose.

Using the 'global' Keyword

The 'global' keyword allows you to modify a global variable from within a function
It tells Python that the variable is global and should not be treated as a local variable
Use 'global' with caution, as it can make your code harder to understand and maintain

Here's an example of using the 'global' keyword:

count = 0

def increment():
    global count
    count += 1
    print(f"Count is now: {count}")

increment()
increment()
increment()
            

Your task:

Create a global variable called 'balance' with an initial value of 1000
Create a function called 'deposit' that takes an amount and adds it to the balance
Create a function called 'withdraw' that takes an amount and subtracts it from the balance
Use both functions a few times and print the final balance

Starter code

# Create a simple banking system using global variables

Write your code here

Weekly Project: Weather Forecast App

Let's put everything we've learned about modules and scope into practice by creating a simple weather forecast app.

Your task is to create a program that:

Creates a custom module called 'weather.py' with functions for different weather conditions
Uses the random module to generate random weather conditions
Keeps track of the current temperature as a global variable
Allows the user to check the weather for different days of the week

Here's a starting template:

# weather.py
import random

def sunny():
    return "It's a sunny day!"

def rainy():
    return "It's raining today."

def cloudy():
    return "It's a cloudy day."

def get_random_weather():
    conditions = [sunny, rainy, cloudy]
    return random.choice(conditions)()

# main.py
import weather

temperature = 20  # Global variable for temperature

def check_weather(day):
    global temperature
    temperature += random.randint(-5, 5)
    condition = weather.get_random_weather()
    return f"{day}: {condition} Temperature: {temperature}°C"

# Test your Weather Forecast App
days = ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday"]

for day in days:
    print(check_weather(day))
            

Enhance the Weather Forecast App by adding the following features:

Add more weather conditions (e.g., snowy, windy) to the weather.py module
Create a function to calculate the average temperature for the week
Add a feature to find the warmest and coldest days of the week
Implement error handling for invalid inputs (e.g., checking weather for an invalid day)

This project will give you hands-on experience with modules, scope, and practical application of Python concepts. Good luck!

Starter code

# Implement your enhanced Weather Forecast App here

Write your code here

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