Namespace Packages (PEP 420 Split Packages)

1Concept

PEP 420 introduced implicit Namespace Packages in Python 3.3+. Directories without `__init__.py` can share a common top-level package namespace across multiple separate project repositories and installation paths (e.g. `azure.storage` and `azure.identity`).

2Architecture Diagram

Repo 1: company/service_a/core.py
Repo 2: company/service_b/core.py
Client imports: `import company.service_a` and `import company.service_b` seamlessly!

3Code Example

import sys
from pathlib import Path

# Inspecting namespace package characteristics
print("Namespace Package Rule (PEP 420):")
print("- Omit __init__.py across split directories.")
print("- CPython dynamically creates a _NamespacePath spanning multiple directories.")

4Expected Output

Namespace Package Rule (PEP 420):
- Omit __init__.py across split directories.
- CPython dynamically creates a _NamespacePath spanning multiple directories.

5Key Takeaways

• ✓Namespace packages lack `__file__` attribute because they do not correspond to a single file.
• ✓Their `__path__` is a dynamic iterable (`_NamespacePath`) rather than a simple list.
• ✓Standard practice for large monorepos and multi-repo enterprise SDK suites.