Python Packages Revisited

Python Packages Revisited

I have always struggled with managing Python packages, especially as I end up with long chains of relative imports like from ...thing import stuff, but it turns out that a Python package always knows the root package name, and can access things from the root package downward via from package.things.thing import stuff

[!NOTE]

• Trying to run a Python script within the package, without calling it via the package itself will run into errors that mention no known parent package
• By default you execute a package via python -m package.module_name
• If the package has a __main__.py then you can use python -m package and this will execute the code in package.__main__

An example directory for a Python package that uses the package.module syntax can be found below. It uses __init__.py files to expose functions from within folders for easier access from package, and lays out the possibilty of a core directory of features that all modules within the package can access with ease

Directory Tree

project/
└── package/
    ├── core/
    │   ├── features.py
    │   └── __init__.py
    ├── tools/
    │   ├── things.py
    │   └── __init__.py
    ├── __init__.py
    └── __main__.py

package/

package/
├── core/
├── tools/
├── __init__.py
└── __main__.py

__init__.py

"""Serves as the public API for the package"""
# < =======================================================
# < Imports
# < =======================================================

from .core import feature
from .tools import thing

__main__.py

"""Package entry point, accessed via python -m package"""
# < =======================================================
# < Imports
# < =======================================================

from .tools import thing

# < =======================================================
# < Execution
# < =======================================================

thing()

core/

core/
├── features.py
└── __init__.py

__init__.py

"""Expose features to be accessed via package.core"""
# < =======================================================
# < Imports
# < =======================================================

from .features import feature

features.py

"""Features to be exported via package/core/__init__.py"""
# < =======================================================
# < Features to be Exported
# < =======================================================

def feature() -> None:
    """Feature function to print information"""
    print("You have called function 'feature'")
    print("This function is accessible via package.core")
    print("This function is accessible via package.core.features")

tools/

tools/
├── things.py
└── __init__.py

__init__.py

"""Expose features to be accessed via package.tools"""
# < =======================================================
# < Imports
# < =======================================================

from .things import thing

things.py

"""Things to be exported via package/tools/__init__.py"""
# < =======================================================
# < Imports
# < =======================================================

from package.core import feature

# < =======================================================
# < Things to be Exported
# < =======================================================

def thing() -> None:
    """Thing function to print information"""
    print("You have called function 'thing'")
    print("This function is accessible via package.tools")
    print("This function is accessible via package.tools.things")
    print("Preparing to call package.core.features.feature()\n")
    feature()