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Learn Python 3: Comprehensive Programming Guide

Creating Your Own Modules

Explore how to organize Python code by creating and using your own modules, separating functionality into multiple files for clarity and reuse. Understand Python's import system, module caching, and how to reload modules during development. This lesson equips you to build modular, maintainable Python applications.

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Designing software follows the same principle as organizing tools in a workshop. If all tools are thrown into one pile, it becomes difficult to find what you need or work efficiently. Likewise, placing all program logic in a single file makes the code harder to read, test, and maintain. Modules group related functionality into separate files. This structure makes the code easier to understand, test, and reuse across different parts of the project without duplication.

Your first custom module

In Python, a module is simply a file ending in .py. A module does not require special declaration syntax; the file name defines the module name. When organizing code, developers typically place definitions, functions, and variables in a module file and use a main file to import the module and run the program logic.

Let's create a simple utility module to handle text operations. We will name this file text_utils.py.

Python 
# text_utils.py
def shout(text):
    """Returns the text in uppercase with an exclamation mark."""
    return f"{text.upper()}!"
def whisper(text):
    """Returns the text in lowercase with an ellipsis."""
    return f"{text.lower()}..."
platform_name = "Educative Text Engine"

Now, we create a separate file ...