pyio-effect 0.1.1

Tiny IO/Try-like effect wrapper for Python.

PyIO - Python Effects System

A lightweight monadic effects system for Python that provides safe error handling and functional composition. PyIO wraps values and exceptions, allowing you to chain operations without explicit error checking at each step.

Overview

PyIO acts like a Try type - it can hold either a successful value or a captured exception. Operations are automatically skipped if a previous step failed, and errors propagate through the chain until handled.

Core Concept

from pyio import PyIO

# Success case
result = PyIO("hello").map(str.upper).get()  # "HELLO"

# Error case - division by zero is captured and propagated
result = PyIO(10).map(lambda x: x // 0).get_or_else(42)  # 42

Operators

Transformation Operators

• map(func) - Transform the value if successful, capture any exceptions thrown by func
• flat_map(func) - Transform with a function that returns a PyIO, flatten the result
• filter(predicate) - Keep value only if predicate returns True, otherwise become empty

Recovery Operators

• recover(func) - Handle errors by providing a recovery function that takes the exception
• recover_with(func) - Handle errors with a function that returns a PyIO

Conditional Operators

• when(predicate, func) - Apply func only if predicate returns True

Side-Effect Operators

• on_success(func) - Execute a side-effect function if the PyIO contains a value
• on_error(func) - Execute a side-effect function if the PyIO contains an error

Extraction Operators

• get() - Extract the value (unsafe - throws if there was an error)
• get_or_else(default) - Extract the value or return default if error/None

Usage Examples

Basic Chaining

result = (PyIO("hello world")
          .map(str.upper)
          .map(lambda s: s + "!!!")
          .get())  # "HELLO WORLD!!!"

Error Handling

result = (PyIO(10)
          .map(lambda x: x // 0)  # ZeroDivisionError captured
          .recover(lambda ex: 999)  # Recover with default value
          .map(lambda x: x * 2)
          .get())  # 1998

Conditional Processing

result = (PyIO(15)
          .when(lambda n: n > 10, lambda n: n * 100)
          .get())  # 1500

Installation

Simply copy the pyio.py file to your project directory and import:

from pyio import PyIO

License

This project is open source. See the license file for details.