How to create a package in Python?

Creating a package in Python involves several steps:

1. Creating the package directory. The directory name will be the package name.

2. Creating the __init__.py file. This file makes the directory a package. It can be empty but is often used for:

   • Package initialization.
   • Defining __all__ for import control.
   • Importing submodules or objects into the package.

3. Creating modules (.py files) inside the package directory. Each .py file inside the package is a module.

4. (Optional) Creating subpackages. Other directories with __init__.py files inside the main package.

5. (Optional) Creating supporting files. For example, README.md, LICENSE, setup.py.

Example structure:

my_package/
├── __init__.py
├── module_a.py
├── module_b.py
└── sub_package/
    ├── __init__.py
    └── module_c.py

File contents:

#__init__.py
# You can import something from modules directly
from .module_a import my_function_a

__all__ = ['my_function_a'] # Defines what is imported with 'from my_package import *'

#module_a.py
def my_function_a():
    print("Hello from module A!")

#module_b.py
def my_function_b():
    print("Hello from module B!")

#sub_package/__init__.py
# Import from a module inside the subpackage
from .module_c import my_function_c

#sub_package/module_c.py
def my_function_c():
    print("Hello from module C in sub_package!")

Using the package:

# In another file outside the my_package directory
# Import a module
import my_package.module_b
my_package.module_b.my_function_b()

# Import a function directly (if it is in __all__ or explicitly imported in __init__.py)
from my_package import my_function_a
my_function_a()

# Import from a subpackage
from my_package.sub_package import my_function_c
my_function_c()