6 2 Creating Modules Explained

Key Concepts

Creating modules in Python involves several key concepts:

• Defining a Module
• Importing a Module
• Using Functions and Variables from a Module
• Module Search Path
• Executing Modules as Scripts

1. Defining a Module

A module in Python is a file containing Python definitions and statements. The file name is the module name with the suffix .py appended.

Example:

# my_module.py
def greet(name):
    return f"Hello, {name}!"

PI = 3.14159
    

Analogy: Think of a module as a toolbox containing various tools (functions and variables) that you can use in your projects.

2. Importing a Module

To use the functions and variables defined in a module, you need to import the module. This is done using the import statement.

Example:

import my_module

print(my_module.greet("Alice"))  # Output: Hello, Alice!
print(my_module.PI)  # Output: 3.14159
    

Analogy: Importing a module is like taking a specific toolbox from a storage room to your workbench.

3. Using Functions and Variables from a Module

Once a module is imported, you can access its functions and variables using the dot notation.

Example:

import my_module

greeting = my_module.greet("Bob")
print(greeting)  # Output: Hello, Bob!

radius = 5
area = my_module.PI * radius ** 2
print(area)  # Output: 78.53975
    

Analogy: Using functions and variables from a module is like selecting specific tools from the toolbox to perform a task.

4. Module Search Path

When you import a module, Python searches for the module in a list of directories. This list is stored in the sys.path variable.

Example:

import sys

print(sys.path)
    

Analogy: The module search path is like a map that guides Python to find the toolbox (module) in various storage rooms (directories).

5. Executing Modules as Scripts

You can execute a module as a script by running it directly. This is useful for testing and debugging. The __name__ variable helps determine if the module is being run as a script.

Example:

# my_module.py
def greet(name):
    return f"Hello, {name}!"

if __name__ == "__main__":
    print(greet("Alice"))
    

Analogy: Running a module as a script is like using the toolbox to perform a specific task directly, rather than just having it available for future use.

Putting It All Together

By understanding and using modules effectively, you can organize your code into reusable and manageable pieces. Modules are a fundamental aspect of Python programming that enhance code maintainability and reusability.

Example:

# my_module.py
def greet(name):
    return f"Hello, {name}!"

PI = 3.14159

if __name__ == "__main__":
    print(greet("Alice"))

# main.py
import my_module

print(my_module.greet("Bob"))  # Output: Hello, Bob!
print(my_module.PI)  # Output: 3.14159