Python Package

1. What is a Package

A package is a collection of Python modules organized in a directory hierarchy, enabling structured and scalable code organization.

Example structure:

my_package/
│── __init__.py
│── module1.py
│── module2.py

The presence of __init__.py indicates that the directory is a Python package.

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2. Creating a Basic Package

# my_package/module1.py
def greet():
    return "Hello from module1"

# main.py
import my_package.module1

print(my_package.module1.greet())

Packages allow logical grouping of related modules.

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3. Importing from a Package

from my_package.module1 import greet

print(greet())

Enables direct access to specific functions or classes within a package.

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4. Using init.py for Initialization

# my_package/__init__.py
from .module1 import greet

from my_package import greet

print(greet())

__init__.py controls what gets exposed when the package is imported.

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5. Sub-packages Structure

my_package/
│── __init__.py
│── analytics/
│   ├── __init__.py
│   └── stats.py

from my_package.analytics.stats import calculate_mean

Packages can contain nested sub-packages for large systems.

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6. Relative Imports Inside a Package

# analytics/stats.py
from .utils import format_number

Relative imports use:

• . current package

• .. parent package

Ensures internal module cohesion.

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7. Absolute Imports in Packages

from my_package.analytics.stats import calculate_mean

Preferred in production for clarity and maintainability.

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8. Installing External Packages with pip

pip install requests

import requests

response = requests.get("https://api.example.com")
print(response.status_code)

External packages extend Python's functionality.

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9. Viewing Installed Packages

pip list

Displays all packages installed in the Python environment.

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10. Packaging a Custom Project (Setup File)

# setup.py
from setuptools import setup, find_packages

setup(
    name="mypackage",
    version="1.0",
    packages=find_packages()
)

This enables distribution and installation of your package via PyPI or internal repositories.

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