Packages

Every Python file, which has the extension .py, is called a module. Python allows us to organize these modules into structures called packages, which are essentially directories that contain a special __init__.py file.

Packages

Key Concepts of Packages in Python

Definition of Packages: A package is a collection of modules organized in directories. A directory must contain an init.py file (which can be empty) to be recognized as a package.
```
my_package/
├── __init__.py
├── module1.py
└── module2.py
```
Importing Modules from Packages: You can import modules or functions from a package using the dot notation. For example, to import module1 from my_package, you would use:
```
from my_package import module1
```
To import a specific function or class from a module within a package:
```
from my_package.module1 import my_function
```
Sub-packages: Packages can contain sub-packages, which are just packages within packages. Each sub-package must also contain its own __init__.py file.
```
my_package/
├── __init__.py
├── module1.py
├── sub_package/
│   ├── __init__.py
│   └── sub_module.py
```
Importing a module from a sub-package:
```
from my_package.sub_package import sub_module
```
Relative Imports: Within a package, you can use relative imports to import modules or sub-packages using relative paths. This is useful for referring to modules in the same package or sub-packages.
```
# In my_package/module1.py
from . import module2  # Import module2 from the same package
from .sub_package import sub_module  # Import sub_module from sub_package
```
Namespace Packages: Starting with Python 3.3, the __init__.py file is no longer required to create a package. This allows for namespace packages, which can span multiple directories. However, the traditional method with __init__.py is still widely used.
```
# Namespace package
my_namespace/
└── my_package/
    └── module1.py
```
Installing External Packages: Python has a robust ecosystem of external packages that can be installed using package managers like pip. These packages are typically hosted on repositories like PyPI (Python Package Index).
```
pip install requests
```
After installation, you can use the installed package in your code:
```
import requests
response = requests.get("https://example.com")
```

Creating and Distributing Packages: To create your own package, you can include a setup.py file with metadata and dependencies. This file is used for packaging and distributing your code.

# setup.py example
from setuptools import setup, find_packages

setup(
    name='my_package',
    version='0.1',
    packages=find_packages(),
    install_requires=[
        'requests',
    ],
)

You can then build and distribute the package using:

python setup.py sdist bdist_wheel
pip install .

Notes about Python

Packages

Key Concepts of Packages in Python