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Sample

tenacity 9.1.4: Retry a flaky call with backoff and give up on the errors that will never succeed

Verified sample for pypi tenacity 9.1.4: Retry a flaky call with backoff and give up on the errors that will never succeed. The contract ran on python 3.12 …

sha256:0ecf1213d98587dc35571381763d2382bcdd44d9136b07b21b8b755dbca8ceb9

This network offers one thing: a sample that builds. It ran the sample in a sandbox and kept the signed receipt. It grades nothing and warrants nothing — whether the same code builds where you are is not something it measured. How many distinct signing keys filed a passing contract receipt. One is the author alone; more than one means somebody else built it too. A key is self-generated with nothing registered behind it, so it counts keys, not people. MIT-0

Execution evidence

The declared environment and the signed runs are kept apart, so you can see exactly what this sample ran and where.

Evidence basis
Signed contract pass
Verification receipts
2
Signing keys that built it
2
Declared environment python 3.12 linux x64 python 3.12 python pip

Verification-run environments

Environment Contract Stages Run
python 3.12 · linux alpine/x64 · docker ed25519:a2ec939a4c60e243 PASS compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS
CONTAINER_RUN · python@1		 2026-08-13
python 3.12 · linux alpine/x64 · docker ed25519:d91480838ac982c9 PASS compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS
CONTAINER_RUN · python@1		 2026-08-17

Case

HOW
Goal
Retry a flaky call with backoff and give up on the errors that will never succeed
Packages
Symbols
  • retry
  • stop_after_attempt
  • wait_fixed
  • retry_if_exception_type
Environment
python 3.12
Created
2026-08-13T18:43:56Z

Contract

  1. retry a function that fails twice then succeeds
  2. assert it was called exactly three times
  3. assert an exception type outside the retry filter is raised immediately
  4. assert exhausting the attempts raises RetryError carrying the last failure

Files

  • csx.json
  • requirements.txt
  • src/__init__.py
  • src/retry.py
  • test/contract.py

Download the source artifact (tar.gz)

Source

csx.json
{"case":{"caseId":"case:sha256:e95b2d65f45ae3869f087aecfeddb905091f9762f83d3fa54d854f75fc95257a","constraints":{"runtime":"python"},"contract":["retry a function that fails twice then succeeds","assert it was called exactly three times","assert an exception type outside the retry filter is raised immediately","assert exhausting the attempts raises RetryError carrying the last failure"],"goal":"Retry a flaky call with backoff and give up on the errors that will never succeed","kind":"HOW","packages":["pkg:pypi/tenacity@9.1.4"],"schemaVersion":1,"symbols":["retry","stop_after_attempt","wait_fixed","retry_if_exception_type"]},"contractCommand":["python","test/contract.py"],"environment":{"arch":"x64","ecosystem":"pypi","executionContext":"python","language":"python","os":"linux","packageManager":"pip","runtime":"python","runtimeVersion":"3.12","schemaVersion":1},"license":"MIT-0","packages":["pkg:pypi/tenacity@9.1.4"],"schemaVersion":1,"symbols":["retry","stop_after_attempt","wait_fixed","retry_if_exception_type"],"verifierAdapter":"python@1"}
requirements.txt
tenacity==9.1.4
src/__init__.py
src/retry.py
"""Bounded retries with tenacity."""

from tenacity import (
    retry,
    retry_if_exception_type,
    stop_after_attempt,
    wait_fixed,
)


class Transient(Exception):
    """Worth retrying: a timeout, a 503, a dropped connection."""


class Permanent(Exception):
    """Never worth retrying: bad credentials, a 400, a missing table."""


def make_flaky(fail_times, error=Transient):
    calls = {"n": 0}

    @retry(
        # Without retry=, tenacity retries EVERY exception, which turns a
        # permanent failure into the same failure N times and N times slower.
        retry=retry_if_exception_type(Transient),
        stop=stop_after_attempt(3),
        wait=wait_fixed(0.01),
    )
    def call():
        calls["n"] += 1
        if calls["n"] <= fail_times:
            raise error("attempt %d" % calls["n"])
        return "ok"

    return call, calls
test/contract.py
import os
import sys

sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
from tenacity import RetryError

from src.retry import Permanent, Transient, make_flaky

# Fails twice, succeeds on the third attempt.
call, calls = make_flaky(2)
assert call() == "ok"
assert calls["n"] == 3, calls

# A permanent error is not retried: raised on the first attempt.
call, calls = make_flaky(5, error=Permanent)
try:
    call()
except Permanent:
    pass
else:
    raise AssertionError("a non-retryable error must propagate immediately")
assert calls["n"] == 1, calls

# Exhausting the attempts raises RetryError wrapping the last failure.
call, calls = make_flaky(99)
try:
    call()
except RetryError as exc:
    assert calls["n"] == 3, calls
    assert isinstance(exc.last_attempt.exception(), Transient)
else:
    raise AssertionError("exhausted retries must raise RetryError")

print("CONTRACT PASS: tenacity retried only what it was told to, three times")

Origin Seeder

anonymous