pyinterfaces 0.5.2

Interface in POO with Python

pyinterfaces

A lightweight Python compiler extension that brings clean, Java-style interface syntax to Python using native braces {}.

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📐 Why pyinterfaces? (Software Engineering Perspective)

In modern Software Engineering, separating definition from implementation is a core architectural principle. Following SOLID principles—specifically the Interface Segregation Principle (ISP) and the Dependency Inversion Principle (DIP)—software components should depend on abstractions (interfaces), not on concrete logic.

While standard Python uses abc.ABC and @abstractmethod to enforce contracts, the syntax can often look cluttered, repetitive, and conceptually muddy (as Python abstract classes can accidentally mix actual logic with abstract models).

pyinterfaces bridges this gap by enforcing Pure Interfaces. It allows software engineers to declare strict structural contracts using the familiar, elegant, and universally understood Java/C# layout, keeping your architecture clean and highly readable.

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✨ Features

• Java-Style Syntax: Declare structures using Interface Name { ... }.
• Pure Abstraction: No mixed implementation code allowed inside the contract block.
• Runtime Enforcement: Automatically triggers native Python abc validations under the hood.
• Zero Overhead: Translated seamlessly during file tokenization using custom stream decoding.

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🚀 Installation

You can install pyinterfaces via pip or add it to your project using poetry:

pip install pyinterfaces

Or with Poetry:

poetry add pyinterfaces

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💻 Usage

To enable the custom Java-like syntax parsing, you must include the magic encoding comment # -*- coding: java_interface -*- at the very first line of your Python script.

Here is a standard example of designing a decoupled Payment System:

# -*- coding: java_interface -*-
import pyinterfaces

# 1. Define the pure architectural contract
Interface PaymentProcessor {
    process_payment(self, amount: float) -> bool
    refund_payment(self, transaction_id: str) -> None
}

# 2. Implement the contract in standard Python classes
class PixProcessor(PaymentProcessor):
    def process_payment(self, amount: float) -> bool:
        print(f"Processing R\${amount} instantly via Pix.")
        return True

    def refund_payment(self, transaction_id: str) -> None:
        print(f"Refunding transaction {transaction_id}.")

# 3. Compile-time / Runtime validation
class BrokenProcessor(PaymentProcessor):
    def process_payment(self, amount: float) -> bool:
        return True
    # ERROR! Missing 'refund_payment' method implementation.

If a developer attempts to instantiate BrokenProcessor, Python will instantly raise a TypeError, stating that the class failed to implement the strict contract requirements defined by your interface.

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🛠️ How it works under the hood

pyinterfaces hooks directly into Python's native codecs registry. When the interpretator reads the # -*- coding: java_interface -*- header, it streams your file through our custom pre-processor, safely transforming the custom block syntax into fully valid standard Python abc.ABC structures before the code even executes.

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👤 Author

• Created and maintained by Bruno Zolotareff
• PyPI Repository: https://pypi.org

🤝 Acknowledgments

Special thanks to my friend Leandro Reginaldo for collaborating on the original concept, brainstorming the architectural ideas, and helping to shape the vision of pyinterfaces. This project wouldn't be the same without your insights!

📄 License

This project is licensed under the MIT License.