Importing Modules

Packages and __init__.py

Python packages are a way of organizing related modules into a hierarchical structure. This helps manage complexity in larger projects. The key to creating a package is the __init__.py file.

• __init__.py: This file (even if it’s empty!) signals to Python that a directory should be treated as a package. Without it, Python treats the directory as just a directory, not a package. It can also contain initialization code for the package, for example, importing specific modules or defining variables to be used throughout the package.

# mypackage/__init__.py
__all__ = ["module1", "module2"]] # This line controls what gets imported with `from mypackage import *`

# Or, you can explicitly import modules to make them available:
from .module1 import *
from .module2 import some_function 

• Structure: A typical package structure looks like this:

mypackage/
├── __init__.py
├── module1.py
└── module2.py

• Importing from Packages:

  • Import specific modules: import mypackage.module1
  • Import specific items: from mypackage.module1 import some_function
  • Import all (using __all__ in __init__.py): from mypackage import * (generally discouraged, it can lead to name clashes)
  • Using relative imports (within the package itself): from .module2 import another_function (the . refers to the current package directory).

• Nested Packages: You can nest packages within packages to create a deeper, more organized hierarchy. Each subpackage needs its own __init__.py file.

mypackage/
├── __init__.py
├── subpackage1/
│   ├── __init__.py
│   └── module3.py
└── subpackage2/
    └── __init__.py
    └── module4.py

• Namespaces and Scope (Linked Note: This would discuss how packages create their own namespaces.)
• Relative vs. Absolute Imports (Linked Note: This would compare and contrast these types of import statements.)
• Circular Imports (Linked Note: This is a common problem when working with packages - this note would describe them and offer solutions.)