Modules and Packages in Python

In Python, modules and packages help organize code into manageable, reusable components. Modules contain functions, classes, and variables, while packages group related modules for better code organization.

1. What is a Module?

A module is simply a Python file (.py) that contains definitions for functions, variables, and classes. Modules make it easy to reuse code across different parts of a project or between projects.

Creating and Using a Module

# In a file named my_module.py
def greet(name):
    return "Hello, " + name

To use this module in another file, use the import statement:

# In another Python file
import my_module
print(my_module.greet("Alice"))

Modules Quiz

What is the file extension for Python modules?

.txt
.py
.mod

How do you access a function from an imported module?

Directly by name
Using dot notation (module.function)
With the call() method

2. What is a Package?

A package is a directory containing a collection of modules. Packages allow for a hierarchical organization of modules, which is especially useful for larger applications. Packages are identified by an __init__.py file in their directory.

Creating a Package

To create a package named my_package with a module my_module.py:

my_package/
├── __init__.py
└── my_module.py

The __init__.py file makes my_package a package and can be empty or contain initialization code for the package.

Using a Package

To use a module from a package, use dot notation:

# In another Python file
from my_package import my_module
print(my_module.greet("Alice"))

Packages Quiz

What file identifies a directory as a Python package?

__init__.py
package.py
main.py

How do you import a module from a package?

import my_module from my_package
from my_package import my_module
require my_package.my_module

3. Importing Modules and Packages

Python offers multiple ways to import modules:

import module_name: Imports the module, accessed with module_name.function().
from module_name import function_name: Imports specific functions or classes directly.
from module_name import *: Imports all functions/classes from the module (not recommended due to potential conflicts).

Example

# Importing a specific function
from my_module import greet
print(greet("Alice"))

Importing Quiz

Which import statement is generally discouraged?

import module
from module import *
from module import specific_function

What's the difference between import module and from module import func?

The first requires module.func(), the second lets you use func() directly
The first is faster than the second
There's no difference

4. Best Practices for Using Modules and Packages

Use Descriptive Names: Choose module and package names that clearly indicate their functionality.
Keep Modules Small: Divide functionality across multiple modules for easier maintenance.
Organize Imports: Use the import convention import statements first, then from imports.
Limit Star Imports: Avoid from module_name import * as it may create conflicts and make debugging harder.

Best Practices Quiz

Why should you avoid from module import *?

It can cause naming conflicts
It makes the code run slower
It's not supported in Python

What's a good practice for module size?

Put all code in one module
Keep modules focused and small
Modules should always be at least 500 lines

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