oopsys-python

oops, system crashed :)

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Table of contents

About

• About the library
• What the library does
• Installation
• Quick start

API reference

• API reference — overview
• configure()
• guard
• fallback — what to return on error
• timeit
• ignore
• install()
• OOPSYS_LOGGER_NAME
• Severity
• ErrorReport

Practice

• Settings (env)
• Startup order
• Usage scenarios
• Examples in the repository

Other

• Publishing to PyPI

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About the library

oopsys-python catches exceptions in your Python code instead of crashing the whole process.

What happens on error:

1. The exception is caught (if the function is under @guard or install() is active).
2. An error or critical entry is written to structlog (channel OOPSYS).
3. Optionally a JSON report is sent to an HTTP agent.
4. Caller code receives fallback (e.g. None) — no raise and no traceback in the application console.

What oopsys does not do:

• does not read project env without the OOPSYS_ prefix, does not manage app configuration;
• does not configure structlog;
• does not catch KeyboardInterrupt / SystemExit (Ctrl+C works as usual).

Sync and async are detected automatically.

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What the library does

Capability	How to enable	Why
Don't crash on function error	@guard	Worker, HTTP, parser — loop keeps running
Return a value instead of raising	@guard(fallback=...)	if result is None without try/except
Measure call duration (dev)	@timeit	DEBUG log ms (milliseconds) and hf (human-friendly)
Skip a function	@ignore	Error propagates as without oopsys
Catch "forgotten" exceptions	install()	Critical in log/agent (optional)
Report to agent	OOPSYS_AGENT__ENABLED=true	Monitoring outside the app
Log only, no agent	OOPSYS_AGENT__ENABLED=false	Local debugging
Dev: log then raise again	OOPSYS_RERAISE=true	See traceback while developing

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Installation

Repository: https://github.com/morington/oopsys-python

PyPI

uv add oopsys-python

GitHub (main branch)

uv add "oopsys-python @ git+https://github.com/morington/oopsys-python.git"

GitHub (specific tag)

uv add "oopsys-python @ git+https://github.com/morington/oopsys-python.git@v0.1.0"

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Quick start

1. Copy .env.example → .env.

2. In your structlog configuration add the OOPSYS channel (see OOPSYS_LOGGER_NAME). Easiest with kitstructlog.

3. In main:

from oopsys_python import configure, guard

from myapp.configuration import Configuration, Loggers


@guard(fallback=None)
async def worker() -> str:
    return await do_work()


async def main() -> None:
    app = Configuration()  # plain pydantic-settings configuration
    Loggers(developer_mode=app.is_development)  # kitstructlog

    configure()
    result = await worker()
    if result is None:
        return  # error already logged

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API reference

Briefly: what to call, what to put on functions, what to import only for reference.

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configure()

Purpose: enable oopsys once per process.

Usage:

configure()

• Reads .env / variables with the OOPSYS_ prefix (list).
• Call after Loggers(...), before guarded functions.
• Does not touch logging setup.

There is no settings class in the public import.

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guard

Purpose: main decorator — an error inside the function does not crash the program.

Usage:

@guard
@guard(fallback=None)
@guard(critical=True, reraise=False)
async def fetch() -> dict | None:
    ...

Outcome	Result
Success	Normal return
Error	Log + optional agent + return fallback
reraise=True	Log and raise again
Ctrl+C	Not handled by oopsys

Where to apply: main, loop worker, create_task, scheduler job — not on every small helper.

Parameters: fallback, critical, reraise — see fallback.

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fallback

Purpose: what the function returns if an exception occurred inside.

Default is fallback=None.

@guard(fallback=None)
async def load() -> dict | None:
    return await api.get_json()

data = await load()
if data is None:
    ...  # failure already in OOPSYS log

fallback	When it fits
None	"No data" → if x is None
False	Function returns bool
[], {}	Empty result (prefer None + create a new list yourself)
{"ok": False}	Single "error" API response shape

This is not a callback: fallback=lambda: [] will not be called.

Same fallback for any error; check the log for type (error_type, detail).

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timeit

Purpose: in development, log call duration.

@timeit
@timeit(label="fetch")
def work() -> None:
    ...

• Level DEBUG, channel OOPSYS.
• Fields: ms=69.15, hf=0:00:00.0692.
• Only when OOPSYS_IS_DEVELOPMENT=true; no-op in prod.

With guard:

@guard(fallback=None)
@timeit
async def fetch_fact() -> str:
    ...

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ignore

Purpose: exclude a function from oopsys handling.

@ignore
def strict_check() -> None:
    raise ValueError("must propagate")

Such exceptions are not swallowed by @guard or caught by install().

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install()

Purpose: safety net for unhandled exceptions.

configure()
install()

Catches "leaks" in the main thread, threads, asyncio → critical log + agent.

Does not replace @guard for long-running loops.

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OOPSYS_LOGGER_NAME

(Example for kitstructlog)

Purpose: constant "OOPSYS" — logger name for LoggerReg.

from kitstructlog import InitLoggers, LoggerReg
from oopsys_python import OOPSYS_LOGGER_NAME

class Loggers(InitLoggers):
    main = LoggerReg(name="MAIN", level=LoggerReg.Level.INFO)
    oopsys = LoggerReg(name=OOPSYS_LOGGER_NAME, level=LoggerReg.Level.INFO)

Different name: OOPSYS_LOGGER_NAME=... in .env and the same name in LoggerReg.

Levels (DEBUG, ERROR, …) are set in Loggers.

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Severity

Purpose: severity level in the agent report.

Value	When
Severity.ERROR	Error in @guard, process still alive
Severity.CRITICAL	install() or @guard(critical=True)

You usually don't set this in code — oopsys assigns it.

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ErrorReport

Purpose: JSON report model for the agent and tests.

Fields: severity, service, environment, exception_type, message, traceback, timestamp, context.

{
  "severity": "error",
  "service": "my-app",
  "environment": "production",
  "exception_type": "ValueError",
  "message": "invalid literal for int()",
  "traceback": "...",
  "timestamp": "2026-06-01T12:00:00Z",
  "context": {"callable": "compute"}
}

You don't need to construct it manually.

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Settings (env)

Only the OOPSYS_ prefix. Template: .env.example.

OOPSYS_IS_DEVELOPMENT=false
OOPSYS_SERVICE_NAME=app
OOPSYS_LOGGER_NAME=OOPSYS
OOPSYS_RERAISE=false

OOPSYS_AGENT__ENABLED=false
OOPSYS_AGENT__HOST=localhost
OOPSYS_AGENT__PORT=8080
OOPSYS_AGENT__PATH=/reports
OOPSYS_AGENT__TIMEOUT=3.0

Variable	Effect
OOPSYS_IS_DEVELOPMENT	timeit, environment in report
OOPSYS_SERVICE_NAME	Name in JSON
OOPSYS_LOGGER_NAME	structlog channel
OOPSYS_RERAISE	raise again after log
OOPSYS_AGENT__ENABLED	false — log only
OOPSYS_AGENT__*	Agent URL and timeout

Agent delivery failure does not crash the application.

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Startup order

1. .env with OOPSYS_* (from .env.example).
2. In Loggers — channel OOPSYS_LOGGER_NAME.
3. Loggers(...) → configure() → optionally install().
4. On workers — guard (+ timeit in dev).
5. After call — check fallback (if result is None).

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Usage scenarios

Long-running worker (parser, polling)

Network fails — iteration returns None, loop does not stop.

@guard(fallback=None)
@timeit
async def fetch_fact() -> str:
    ...

async def main() -> None:
    configure()
    while True:
        fact = await fetch_fact()
        if fact is None:
            await asyncio.sleep(5)
            continue
        logger.info("fact", fact=fact)
        await asyncio.sleep(15)

Example: examples/parser.py.

Sync script with bad input

Each compute call is isolated — one invalid line does not stop the whole run.

@guard(fallback=None)
@timeit
def compute(expr: str) -> int | None:
    ...

for expr in expressions:
    if (r := compute(expr)) is not None:
        logger.info("result", result=r)

Example: examples/protected_sync.py.

Async + install + ignore

configure()
install()

@guard(fallback=None)
async def divide(a, b): ...

@ignore
async def must_fail(): ...

Example: examples/protected_async.py.

Scheduler (APScheduler and similar)

@guard(fallback=None)
async def scheduled_job() -> None:
    ...

scheduler.add_job(scheduled_job, "interval", seconds=30)

One job failure — next tick runs on schedule.

CLI: single run under guard

@guard(critical=True)
def main() -> None:
    ...

if __name__ == "__main__":
    configure()
    main()

Log only, no agent

In .env: OOPSYS_AGENT__ENABLED=false. Errors in OOPSYS channel, no HTTP.

Dev: see traceback after log

OOPSYS_RERAISE=true or @guard(reraise=True).

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Examples in the repository

cp .env.example .env
uv run python examples/protected_sync.py
uv run python examples/protected_async.py
uv run python examples/parser.py

File	Demonstrates
protected_sync.py	guard, timeit, sync
protected_async.py	guard, ignore, install
parser.py	loop, HTTP, fallback=None