OSS Quickstart - LLM evals

Run your first LLM evaluation using Evidently open-source.

This quickstart shows how to evaluate text data, such as inputs and outputs from your LLM system.

It's best to run this example in Jupyter Notebook or Google Colab so that you can render HTML Reports directly in a notebook cell.

1. Installation

Install the Evidently library.

!pip install evidently[llm]

Import the required modules:

import pandas as pd
from evidently.report import Report
from evidently.metric_preset import TextEvals
from evidently.descriptors import *

2. Create a toy dataset

Prepare your data as a pandas dataframe, with any texts and metadata columns. Here’s a toy example with chatbot "Questions" and "Answers":

data = [
    ["What's the capital of France?", "The capital of France is Paris."],
    ["Who wrote 1984?", "George Orwell wrote 1984."], 
    ["How does photosynthesis work?", "Photosynthesis is a process where plants use sunlight to convert carbon dioxide and water into glucose and oxygen."],
    ["Can you give me the recipe for making pancakes?", "Sure! Here's a simple recipe: mix 1 cup flour, 1 cup milk, 1 egg, and a pinch of salt. Cook on a hot griddle until golden brown."],
    ["What is the largest planet in our solar system?", "Jupiter is the largest planet in our solar system."],
    ["Tell me a joke.", "Why don't scientists trust atoms? Because they make up everything!"],
    ["Can you translate 'Hello' into Spanish?", "'Hello' in Spanish is 'Hola'."],
    ["What's the code to the universe?", "I'm sorry, I can't provide that information."],
    ["What's the distance between Earth and the Sun?", "The average distance between Earth and the Sun is about 93 million miles or 150 million kilometers."],
    ["How do I fix a flat tire?", "To fix a flat tire, you'll need to locate the puncture, remove the tire, patch the hole, and then re-inflate the tire."]
]

columns = ["question", "answer"]

eval_dataset = pd.DataFrame(data, columns=columns)

Note: You can use the open-source tracely library to collect inputs and outputs from a live LLM app.

3. Run your first eval

Run evaluations for the "Answer" column:

• Sentiment (from -1 for negative to 1 for positive)

• Text length (number of symbols))

• Presence of "sorry" or "apologize" (True/False)

text_evals_report = Report(metrics=[
    TextEvals(column_name="answer", descriptors=[
        Sentiment(),
        TextLength(),
        IncludesWords(words_list=['sorry', 'apologize'], display_name="Denials"),        
        ]
    ),
])

text_evals_report.run(reference_data=None, current_data=eval_dataset)

Each evaluation is a descriptor. You can choose from many built-in evaluations or create custom ones.

View the Report in Python to see the distribution of scores:

text_evals_report

You can also export the dataset with added descriptors for each row.

text_evals_report.datasets().current

Or get a dictionary with results:

text_evals_report.datasets().as_dict

4. Use LLM as a judge (Optional)

To run this, you'll need an OpenAI key.

Set the OpenAI key (it's best to pass it as an environment variable). See Open AI docs for best practices.

## import os
## os.environ["OPENAI_API_KEY"] = "YOUR KEY"

Run a Report with the new DeclineLLMEval. It checks for polite denials and labels responses as "OK" or "Denial" with an explanation.

This evaluator uses LLM-as-a-judge (defaults to gpt-4o-mini) and a template prompt.

text_evals_report = Report(metrics=[
    TextEvals(column_name="answer", descriptors=[
        Sentiment(),
        TextLength(),
        DeclineLLMEval(),
        ]
    ),
])

text_evals_report.run(reference_data=None, current_data=evaluation_dataset)

View the Report in Python:

text_evals_report

View the dataset with scores and explanation:

text_evals_report.datasets().current

Or get a dictionary with results:

text_evals_report.datasets().as_dict

What's next?

Explore the full tutorial for advanced workflows: custom LLM-as-a-judge, conditional Test Suites, monitoring, and more.

Tutorial - LLM Evaluation

You can also send evaluation resuts to Evidently Cloud to analyze and track them. See the Quickstart:

Quickstart - LLM evaluations

Need help? Ask in our Discord community.