Department SQL Class Exercise

Hands-On Exercises: Python Modules & Packages

Exercise : Create Your String Tools Functions

Goal: Write simple functions that we’ll later turn into a module

Create a new file called string_tools.py and write these functions:

def reverse_string(text):
    """
    Reverse a string
    Example: reverse_string("hello") returns "olleh"
    """
    # Your code here
    pass

def count_vowels(text):
    """
    Count vowels (a, e, i, o, u) in a string
    Example: count_vowels("hello") returns 2
    """
    # Your code here
    pass

def is_palindrome(text):
    """
    Check if a string reads the same forwards and backwards
    Example: is_palindrome("racecar") returns True
    """
    # Your code here
    pass

Test your functions by adding this at the bottom of string_tools.py:

if __name__ == "__main__":
    # Test your functions here
    print(reverse_string("hello"))
    print(count_vowels("hello world"))
    print(is_palindrome("racecar"))

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Exercise 2: Use Your Module

Goal: Import and use your functions from another script

Create a new file called main.py in the same folder as string_tools.py:

# Import your functions here
# Try different import styles:
# 1. import string_tools
# 2. from string_tools import reverse_string
# 3. from string_tools import *

# Test your imported functions
test_word = "python"

# Use your functions and print the results

Questions to explore:

• What’s the difference between import string_tools and from string_tools import reverse_string?
• How do you call the functions with each import style?

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Exercise 3: Convert to a Package Structure

Goal: Reorganize your code into a proper package

Create this folder structure:

texttools/               # This is your package folder
├── __init__.py         # Makes it a package
├── string_utils.py     # Move your functions here
└── examples.py         # Example usage

Step by step:

1. Create a folder called texttools
2. Create an empty __init__.py file inside it
3. Move your functions from string_tools.py to texttools/string_utils.py
4. Create texttools/examples.py with some example usage
5. Update texttools/__init__.py to expose your functions:

# In texttools/__init__.py
from .string_utils import reverse_string, count_vowels, is_palindrome

# Optional: define what gets imported with "from texttools import *"
__all__ = ['reverse_string', 'count_vowels', 'is_palindrome']

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Exercise 4: Use Your Package

Goal: Import and use your package from outside its folder

Create a new file called test_package.py outside the texttools folder:

your_project/
├── texttools/           # Your package
│   ├── __init__.py
│   ├── string_utils.py
│   └── examples.py
└── test_package.py      # This file

In test_package.py, try different ways to import:

# Method 1: Import the package
import texttools
result1 = texttools.reverse_string("hello")

# Method 2: Import specific functions
from texttools import count_vowels, is_palindrome
result2 = count_vowels("programming")

# Method 3: Import everything
from texttools import *
result3 = reverse_string("python")

print(f"Reversed: {result1}")
print(f"Vowels: {result2}")
print(f"Reversed again: {result3}")

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Exercise 5: Add More Features to Your Package

Goal: Expand your package with additional functionality

Add a new module texttools/text_stats.py:

def word_count(text):
    """Count words in text"""
    # Your code here
    pass

def char_frequency(text):
    """Return a dictionary of character frequencies"""
    # Your code here
    pass

def longest_word(text):
    """Find the longest word in text"""
    # Your code here
    pass

Update your texttools/__init__.py:

from .string_utils import reverse_string, count_vowels, is_palindrome
from .text_stats import word_count, char_frequency, longest_word

__all__ = [
    'reverse_string', 'count_vowels', 'is_palindrome',
    'word_count', 'char_frequency', 'longest_word'
]

Test your expanded package!

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Bonus Challenge: Make It Installable

Goal: Create a package that can be installed with pip

Create a pyproject.toml file in your project root:

[build-system]
requires = ["setuptools>=45", "wheel"]
build-backend = "setuptools.build_meta"

[project]
name = "texttools-yourname"  # Replace yourname with your actual name
version = "0.1.0"
description = "A simple text processing toolkit"
authors = [{name = "Your Name", email = "your.email@example.com"}]
readme = "README.md"
requires-python = ">=3.7"

[project.urls]
Homepage = "https://github.com/yourusername/texttools"

Install your package in development mode:

pip install -e .

Now you can import your package from anywhere!

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Reflection Questions

1. What’s the difference between a module and a package?
2. Why do we need __init__.py files?
3. When would you use from module import * vs import module?
4. How does Python find your modules and packages?
5. What are the advantages of organizing code into packages?