clean-raise 1.1.2

A simple, zero-dependency utility to raise exceptions as if they originated directly from the invoking method

Introduction

clean_raise is a simple, zero-dependency utility to raise exceptions as if they originated directly from the invoking method.

Supported Versions

• Overall Package Support: Python 3.9 ~ Python 3.15
• Distribution Strategy: This project distributes independent wheel files optimized for specific Python versions.

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Basic Usage

from clean_raise import clean_raise

def func():
    clean_raise(RuntimeError('An error occurred during runtime'))

func()

You will get a traceback like this, entirely skipping the execution frames of clean_raise itself:

Traceback (most recent call last):
  File "(FILEPATH)", line 6, in <module>
    func()
    ~~~~^^
RuntimeError: An error occurred during runtime

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Advanced Usage

clean_raise() accepts an optional bytecode offset parameter, lasti_move, allowing you to manually recalibrate where the traceback indicator points at the bytecode level.

def clean_raise(exception: Any | None = None, lasti_move: int | None = 0, /) -> NoReturn: ...

• exception: The exception instance or class to be raised. If the argument is not an instance or subclass of BaseException, it will be wrapped and raised as RuntimeError(exception). If omitted, it defaults to raising RuntimeError('No active exception to reraise').
• lasti_move: The logical bytecode instruction offset (positive moves forward, negative moves backward). Use this to fine-tune the traceback pointer if it does not align precisely with your target code block.

Note: Although Python code objects group bytes in 2-byte intervals (1 code unit), clean_raise() automatically scales lasti_move internally. Additionally, it skips redundant opcodes (such as CACHE, NOP, and RESUME) for a more intuitive user experience. When passing this argument, please specify the value in increments of 1 logical instruction.

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How It Works

To strip the internal call stack from the traceback, this utility employs low-level and somewhat intrusive runtime operations. Please be aware of the following behaviors when integrating this module:

1. Temporary sys.excepthook Override

To prevent a native raise statement from duplicating the error message on screen, this tool temporarily overrides the global sys.excepthook if clean_raise() is called outside a try-except block.

2. Behavior Within try-except Blocks

• To ensure exceptions can be caught normally within active error-handling scopes, the utility parses the current frame's co_exceptiontable in reverse.
• If it detects that clean_raise was invoked inside a handled block (by checking if lasti falls within a calculated range), it will reraise the exception. This allows the exception to bubble up normally so that external except clauses can capture it correctly.

3. Global Scope Restrictions

clean_raise() relies on traversing back up the execution frames to synthesize the clean traceback. Consequently, it cannot be called directly from the global scope. Violating this constraint will raise the following exception: RuntimeError: clean_raise.clean_raise() cannot be called from the global scope

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Known Issues

1. Behavior in asyncio Environments Differs from Native Errors

Because clean_raise works by traversing and synthesizing frames backward from the caller's context until it reaches the top-level frame (frame is None)—rather than originating the traceback directly from the actual exception trigger point—it will generate tracebacks in an asyncio environment that differ significantly from native raise statements.

2. Traceback Chain Pollution on Caught Exception Objects

Due to Python's native behavior, any raise statement unconditionally appends the current execution frame to the exception's traceback chain. When clean_raise() is caught within a try-except block, it achieves this by triggering a literal raise alongside a temporarily silenced excepthook. Consequently, the resulting exception object will inevitably contain a frame from clean_raise inside its .__traceback__.tb_next chain, causing minor traceback pollution.

3. Lack of Native Threading Support

The current implementation is optimized for the main execution thread and does not yet safely adapt to multi-threaded environments. Because unhandled exceptions within spawning threads are intercepted by threading.excepthook rather than the standard sys.excepthook, invoking clean_raise() inside a separate thread may lead to unexpected tracebacks.

*Full support for multi-threaded contexts is planned for a future release.