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Scoring an experiment

Scoring an experiment means calling metrics inside the @experiment function, so each saved row carries its scores next to the app's answer.

Last updated: 29 Sep, 2026 · RAGAS 0.4.3

An experiment that only records answers still leaves someone to read them. Put the metrics inside it and every run leaves a table of numbers: the video's phase two, one row per golden.

Metrics inside an experiment

python
@experiment()
async def scored(row):
    ...
    faith = await faithfulness.ascore(...)  # ascore, because the function is async
    return {**row, "faithfulness": faith.value}
Project files used on this pageThis lesson builds on a project from earlier lessons. The code below imports these files. Click a file to see its code, or follow the link to the lesson that wrote it. To run the code yourself, keep them in the same folder.
View the code here
judge.py
import os

from google import genai
from openai import AsyncOpenAI
from ragas.embeddings import GoogleEmbeddings
from ragas.llms import llm_factory

groq = AsyncOpenAI(
    api_key=os.environ.get("JUDGE_GROQ", os.environ["GROQ_API_KEY"]),
    base_url="https://api.groq.com/openai/v1",
)
judge = llm_factory("openai/gpt-oss-20b", provider="openai", client=groq)


class OneTextPerCall(GoogleEmbeddings):
    """gemini-embedding-2 turns a list into one embedding, so embed each text on its own."""

    def embed_texts(self, texts, **kwargs):
        return [self.embed_text(text) for text in texts]

    async def aembed_texts(self, texts, **kwargs):
        return [await self.aembed_text(text) for text in texts]


embeddings = OneTextPerCall(client=genai.Client(), model="gemini-embedding-2")
technest.py
import json
import os

import numpy as np
from google import genai
from openai import OpenAI

gemini = genai.Client()  # reads GOOGLE_API_KEY
groq = OpenAI(api_key=os.environ["GROQ_API_KEY"], base_url="https://api.groq.com/openai/v1")
EMBED_MODEL = "gemini-embedding-2"
CHAT_MODEL = "qwen/qwen3.8-27b"

SYSTEM_PROMPT = """You are a helpful customer support assistant for TechNest, an online electronics store.
Answer the customer's question using ONLY the information provided in the context below.
If the context does not contain enough information to answer fully, say so honestly.
Keep your answer concise, factual, and friendly. Do not invent any details not present in the context.
Reply in two or three plain sentences, with no lists or tables."""

with open("catalog.json", encoding="utf-8") as f:
    CATALOG = json.load(f)


def embed(texts):
    # gemini-embedding-2 turns everything in one call into one embedding, so send one text per call
    vectors = np.array([gemini.models.embed_content(model=EMBED_MODEL, contents=t).embeddings[0].values for t in texts])
    return vectors / np.linalg.norm(vectors, axis=1, keepdims=True)


DOC_VECTORS = embed([f"{item['title']}. {item['content']}" for item in CATALOG])


def retrieve(question, top_k=3):
    scores = DOC_VECTORS @ embed([question])[0]
    best = np.argsort(scores)[::-1][:top_k]
    return [CATALOG[i]["content"] for i in best]


def generate(question, contexts):
    context_block = "\n\n".join(f"[{i+1}] {c}" for i, c in enumerate(contexts))
    messages = [
        {"role": "system", "content": SYSTEM_PROMPT},
        {"role": "user", "content": f"Context:\n{context_block}\n\nCustomer question: {question}"},
    ]
    response = groq.chat.completions.create(model=CHAT_MODEL, messages=messages, temperature=0)
    return response.choices[0].message.content.strip()


def answer(question, top_k=3):
    contexts = retrieve(question, top_k)
    return generate(question, contexts), contexts
catalog.json
[
  {
    "id": "prod_001",
    "category": "product",
    "title": "ProBook X1 Laptop",
    "content": "The TechNest ProBook X1 is a 14-inch laptop featuring an Intel Core i7-13th Gen processor, 16GB DDR5 RAM, and a 512GB NVMe SSD. It has a battery life of 12 hours, weighs 1.4kg, and comes with a backlit keyboard. Price: $1,299. Includes a 2-year manufacturer warranty."
  },
  {
    "id": "prod_002",
    "category": "product",
    "title": "PixelPhone 15",
    "content": "The TechNest PixelPhone 15 is a 6.7-inch AMOLED smartphone with a 50MP triple camera system, 8GB RAM, 256GB storage, and a 5,000mAh battery supporting 65W fast charging. Available in Midnight Black and Arctic White. Price: $899. Includes a 1-year warranty."
  },
  {
    "id": "prod_003",
    "category": "product",
    "title": "SoundPods Pro",
    "content": "The TechNest SoundPods Pro are true wireless earbuds with active noise cancellation (ANC), 8 hours of playback per charge plus 24 hours with the case, and IPX4 water resistance. They connect via Bluetooth 5.3 and support multipoint pairing with two devices simultaneously. Price: $149."
  },
  {
    "id": "prod_004",
    "category": "product",
    "title": "UltraTab S2 Tablet",
    "content": "The TechNest UltraTab S2 is a 11-inch tablet powered by a Snapdragon 870 processor with 8GB RAM and 128GB storage expandable via microSD. It features a 120Hz display, a 7,500mAh battery, and supports the TechNest Stylus Pen sold separately. Price: $549. Includes a 1-year warranty."
  },
  {
    "id": "prod_005",
    "category": "product",
    "title": "SmartWatch X",
    "content": "The TechNest SmartWatch X features continuous heart rate monitoring, SpO2 tracking, GPS, and 7-day battery life. It is water-resistant up to 50 metres. Compatible with both Android and iOS. Price: $299. Includes a 1-year warranty and a free extra silicone band."
  },
  {
    "id": "prod_006",
    "category": "product",
    "title": "ProCam 4K Action Camera",
    "content": "The TechNest ProCam 4K shoots 4K video at 60fps and 20MP photos. It is waterproof up to 10 metres without a case, has built-in image stabilisation (EIS), and includes a touch screen. Battery life is 90 minutes of 4K recording. Price: $229. Includes a 1-year warranty."
  },
  {
    "id": "prod_007",
    "category": "product",
    "title": "BassBuds Max Headphones",
    "content": "The TechNest BassBuds Max are over-ear wireless headphones with 40-hour battery life, hybrid active noise cancellation, and a premium 40mm driver for deep bass. They fold flat for travel and include a carrying case. Price: $199. Compatible with all Bluetooth devices."
  },
  {
    "id": "prod_008",
    "category": "product",
    "title": "SoundBar 360",
    "content": "The TechNest SoundBar 360 is a 2.1 soundbar with a 120W output, built-in subwoofer, Dolby Atmos support, and HDMI ARC connectivity. It also supports Bluetooth streaming and has an optical audio input. Dimensions: 90cm wide. Price: $349. Includes a 2-year warranty."
  },
  {
    "id": "policy_001",
    "category": "policy",
    "title": "Return Policy",
    "content": "TechNest accepts returns within 30 days of the original purchase date. Items must be in their original packaging with all accessories included. Customers are responsible for return shipping costs unless the item arrives defective or damaged. Refunds are processed within 5 to 7 business days of receiving the returned item. Digital downloads and opened software are non-refundable."
  },
  {
    "id": "policy_002",
    "category": "policy",
    "title": "Shipping Policy",
    "content": "TechNest offers free standard shipping on all orders over $50 within the continental US. Standard shipping takes 3 to 5 business days. Expedited shipping (1 to 2 business days) is available for $9.99. Same-day delivery is available in select cities for $19.99. Orders placed before 2pm local time are dispatched the same day."
  },
  {
    "id": "policy_003",
    "category": "policy",
    "title": "Warranty Policy",
    "content": "All TechNest products include a minimum 1-year manufacturer warranty covering defects in materials and workmanship. The ProBook X1 and SoundBar 360 include a 2-year warranty. Warranty does not cover physical damage, water damage (unless the product is rated waterproof), or damage from unauthorised modifications. To make a warranty claim, contact support@technest.com with your order number and a description of the issue."
  },
  {
    "id": "policy_004",
    "category": "policy",
    "title": "Payment Policy",
    "content": "TechNest accepts Visa, Mastercard, American Express, PayPal, and Apple Pay. All transactions are encrypted using 256-bit SSL. Buy Now Pay Later is available via Klarna for orders over $100, with 0% interest for 3 monthly instalments. TechNest does not store full card details — payments are processed securely by Stripe."
  },
  {
    "id": "faq_001",
    "category": "faq",
    "title": "Order Tracking",
    "content": "To track your order, visit technest.com/orders and enter your order number and email address. A shipping confirmation email with a tracking link is sent within 24 hours of dispatch. If you have not received your tracking email after 48 hours, check your spam folder or contact support@technest.com."
  },
  {
    "id": "faq_002",
    "category": "faq",
    "title": "International Shipping",
    "content": "TechNest ships to over 40 countries. International shipping rates start at $14.99 and delivery takes 7 to 14 business days. Import duties and taxes are the responsibility of the customer and are not included in the product price. Free shipping promotions apply to US orders only."
  },
  {
    "id": "faq_003",
    "category": "faq",
    "title": "Bulk and Business Orders",
    "content": "TechNest offers volume discounts for businesses purchasing 10 or more units of any single product. Discounts range from 10% for 10 to 49 units up to 25% for 100 or more units. Contact business@technest.com with your requirements for a custom quote. A dedicated account manager is assigned for orders over $10,000."
  }
]
goldens.json
[
  {
    "id": "g001",
    "metric_focus": "faithfulness",
    "user_input": "What is TechNest's return policy?",
    "reference": "TechNest accepts returns within 30 days of purchase. Items must be in original packaging with all accessories. Customers pay return shipping unless the item is defective. Refunds are processed in 5 to 7 business days."
  },
  {
    "id": "g002",
    "metric_focus": "answer_relevancy",
    "user_input": "What are the RAM and storage specs of the ProBook X1?",
    "reference": "The ProBook X1 has 16GB DDR5 RAM and a 512GB NVMe SSD."
  },
  {
    "id": "g003",
    "metric_focus": "context_precision",
    "user_input": "How long is the battery life on the SoundPods Pro?",
    "reference": "The SoundPods Pro offer 8 hours of playback per charge and an additional 24 hours from the charging case, giving a total of 32 hours."
  },
  {
    "id": "g004",
    "metric_focus": "context_recall",
    "user_input": "What are TechNest's shipping options and how long do returns take to process?",
    "reference": "TechNest offers free standard shipping on orders over $50 (3 to 5 business days) and expedited shipping for $9.99 (1 to 2 business days). Returns are accepted within 30 days and refunds are processed in 5 to 7 business days after the item is received."
  },
  {
    "id": "g005",
    "metric_focus": "answer_correctness",
    "user_input": "What is the price of the PixelPhone 15?",
    "reference": "The TechNest PixelPhone 15 is priced at $899."
  }
]

The bug: score() inside an async function

Every metric has two methods, score and ascore. An experiment function is async, and calling the plain score from inside one fails before any judge call is made.

ExampleAPI key
import asyncio

from judge import judge
from ragas.metrics.collections import Faithfulness


async def scored_row():
    return Faithfulness(llm=judge).score(user_input="q", response="a", retrieved_contexts=["c"])


asyncio.run(scored_row())

The message names the fix: inside async code, await metric.ascore(...).

One row at a time

arun starts every row at once, which is the burst the Rate limits and cooldowns lesson warned about. An asyncio.Lock lets one row in at a time, and the sleep inside it is the video's sample cooldown.

python
one_at_a_time = asyncio.Lock()

async with one_at_a_time:
    ...                                   # answer, then score
    await asyncio.sleep(SAMPLE_COOLDOWN)  # pause before the next row gets the lock

The scored row

python
faith = await faithfulness.ascore(user_input=row["user_input"], response=response, retrieved_contexts=contexts)
rec = await recall.ascore(user_input=row["user_input"], retrieved_contexts=contexts, reference=row["reference"])
return {**row, "response": response, "faithfulness": faith.value, "context_recall": rec.value}

Two metrics, one per half of the app: faithfulness for the answer, context recall for the search. The metrics are built once, outside the function, and reused for every row.

Phases one and two over the five goldens

Save this as scoring.py in the folder with datasets/goldens.csv, technest.py, catalog.json and judge.py. It takes about three minutes, most of it cooldowns.

ExampleAPI key
import asyncio

from judge import judge
from ragas import Dataset, experiment
from ragas.metrics.collections import ContextRecall, Faithfulness
from technest import answer

SAMPLE_COOLDOWN = 25
one_at_a_time = asyncio.Lock()
faithfulness = Faithfulness(llm=judge)
recall = ContextRecall(llm=judge)


@experiment()
async def scored(row):
    async with one_at_a_time:
        response, contexts = answer(row["user_input"])
        faith = await faithfulness.ascore(user_input=row["user_input"], response=response, retrieved_contexts=contexts)
        rec = await recall.ascore(user_input=row["user_input"], retrieved_contexts=contexts, reference=row["reference"])
        await asyncio.sleep(SAMPLE_COOLDOWN)
    return {**row, "response": response, "faithfulness": faith.value, "context_recall": rec.value}


dataset = Dataset.load(name="goldens", backend="local/csv", root_dir=".")
rows = sorted(asyncio.run(scored.arun(dataset, name="scored")), key=lambda r: r["id"])
print(len(rows), "rows scored")
for row in rows:
    print(row["id"], f"faithfulness={row['faithfulness']:.2f}", f"context_recall={row['context_recall']:.2f}")
print(f"mean faithfulness:   {sum(r['faithfulness'] for r in rows) / len(rows):.2f}")
print(f"mean context recall: {sum(r['context_recall'] for r in rows) / len(rows):.2f}")

Reading the scored table

  • Five rows scored means no golden was dropped; fewer would mean a row raised and arun left it out.
  • Each row has one score for the answer and one for the search, so a low row tells you which half failed.
  • The means are the numbers to write down before you change anything, so the next run has something to beat.

score() vs ascore()

score()ascore()
Call it fromA plain scriptInside async def, with await
Inside an experimentRaises RuntimeErrorThe one to use
ResultThe same MetricResultThe same MetricResult

When to score inside an experiment

  • Whenever a change should be judged, not only run: prompts, retrievers, models.
  • When the scores must stay attached to the exact answers they judged, in one file.
Watch out. A mean hides the worst rows. Five goldens averaging 0.9 can still include one that scored 0.5. Read the rows, not only the mean; that is what the next lesson's report is for.
Try it yourself
  • Add AnswerRelevancy(llm=judge, embeddings=embeddings) as a third score; import embeddings from judge.
  • Set SAMPLE_COOLDOWN = 0 and remove the lock, run it, and count how many rows come back.
PreviousExperiments

Little by little, you're building something great.