noexcept 1.2.0

A callable interface for structured exceptions

No Exceptions

A callable interface for structured exceptions in Python, allowing dynamic registration of error codes, soft (non-raising) codes, exception propagation with context, and grouping multiple errors.

Features

Dynamic Error Codes: Register custom error codes with default messages at runtime.

Soft Errors: Define codes that don’t immediately raise exceptions, useful for warning accumulation.

Error Propagation: Wrap existing exceptions under new error codes while preserving context.

Exception Linking: Attach underlying exceptions to your custom errors for full traceability.

ExceptionGroup Support: Bundle multiple error codes into a single ExceptionGroup.

Rich String Output: Automatically include codes, messages, linked exceptions, and stack traces when converting to string.

Installation

Requires Python 3.11 or newer.

From PyPI

pip install noexcept

From source

git clone <repo-url>
cd noexcept
pip install .

Quick Start

Import the callable exception handler and register your error codes:

import no

Register codes at startup

no.register(404, "Not Found")            # Standard error
no.register(500, "Server Error")         # Standard error
no.register(123, "Soft Error", soft=True)  # Soft (non-raising)

Raising an Exception

from no.module import no

try:
    no(404)
except no.xcpt as e:
    print(str(e))
    # Output:
    # [404]
    # Not Found

Soft Errors

Soft codes don’t immediately raise:

no(123)  # No exception is thrown because code 123 is registered as soft

Propagating Errors

Wrap an existing exception under a new code:

try:
    raise ValueError("underlying issue")
except ValueError as ve:
    try:
        no(500, ve)  # Raises a no.xcpt with both 500 and linked ValueError
    except no.xcpt as e:
        print(e)

Linking Underlying Exceptions

Add an existing exception to a new code without raising immediately:

try:
    raise KeyError("missing key")
except KeyError as ke:
    no(404, ke, soften=True)

Grouping Multiple Errors

Bundle multiple codes in one go:

try:
    no([404, 500])
except ExceptionGroup as eg:
    for subexc in eg.exceptions:
        print(subexc)

API Reference

no.register(code: int, message: str, soften: bool = False)

Register a new error code.

code: Numeric identifier.

message: Default message for the code.

soften: If True, calling this code won’t raise immediately.

no(code: int | list[int] | Exception, message: str = None, soften: bool = False)

Invoke or raise an error:

Single int: Raise or return a no.xcpt for that code.

list[int]: Raises an ExceptionGroup of all specified codes.

Existing Exception: Links this exception under your codes.

message: Append an extra message to the error.

soften: Suppresses immediate raising for soft usage.

no.xcpt

Base exception type for all registered errors. Inherits rich context and linking support.

Contributing

Contributions are welcome! Please open issues and pull requests on GitHub.

License

This project is licensed under the MIT License. See LICENSE for details.

Authored by Nichola Walch [e-mail]