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Prerequisites:
  • Python 3.10+
  • An API key for an LLM provider (e.g., OpenAI, Anthropic, Google)
This guide will walk you through installing SigmaEval, setting up your first evaluation, and running a “Hello World” example.
Recommended: create and activate a Python virtual environment to avoid dependency conflicts.
Create a Python virtual environment:
python -m venv .venv
Activate the Python virtual environment:
  • Windows CMD
  • Windows Powershell
  • MacOS / Linux
.venv\Scripts\activate.bat

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Installation

First, install the SigmaEval framework from PyPI. 
pip install sigmaeval-framework
You will also need to set your API key for the LLM provider you wish to use for the AI Judge. SigmaEval supports 100+ LLM providers via LiteLLM, including OpenAI, Anthropic, Google, and local models via Ollama. 
export OPENAI_API_KEY="your-api-key"

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Hello World Example

Here is a minimal, complete example of how to use SigmaEval to test a simple AI application. This example evaluates a bot that is expected to return a friendly greeting.
test_app.py
from sigmaeval import SigmaEval, ScenarioTest, assertions
import asyncio
from typing import List, Dict, Any

# 1. Define the ScenarioTest to describe the desired behavior
scenario = (
    ScenarioTest("Simple Test")
    .given("A user interacting with a chatbot")
    .when("The user greets the bot")
    .expect_behavior(
        "The bot provides a simple and friendly greeting.",
        # We want to be confident that at least 75% of responses will score a 7/10 or higher.
        criteria=assertions.scores.proportion_gte(min_score=7, proportion=0.75)
    )
    .max_turns(1) # Only needed here since we're returning a static greeting
)
# 2. Implement the app_handler to allow SigmaEval to communicate with your app
async def app_handler(messages: List[Dict[str, str]], state: Any) -> str:
    # In a real test, you would pass messages to your app and return the response.
    # For this example, we'll return a static, friendly greeting.
    return "Hello there! Nice to meet you!"

# 3. Initialize SigmaEval and run the evaluation
async def main():
    # You can use any model that LiteLLM supports: https://docs.litellm.ai/docs/providers
    sigma_eval = SigmaEval(
        judge_model="gemini/gemini-2.5-flash",
        sample_size=20,  # The number of times to run the test
        significance_level=0.05  # Corresponds to a 95% confidence level
    )
    result = await sigma_eval.evaluate(scenario, app_handler)

    # Print the detailed summary to the console
    print(result)

    # Programmatically check the result
    if result.passed:
        print("✅ Scenario passed!")
    else:
        print("❌ Scenario failed.")

if __name__ == "__main__":
    asyncio.run(main())

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Interpret the Results

When you run the script, SigmaEval will simulate 20 conversations, have an AI Judge score each one, and then print a summary of the results. The summary shows the overall pass/fail status for the scenario and a breakdown of each expectation. Here’s an example of what the output might look like: 
--- Result for Scenario: 'Simple Test' ---
Overall Status: ✅ PASSED
Summary: 1/1 expectations passed.

Breakdown:
  - [✅ PASSED] The bot provides a simple and friendly greeting., p-value: 0.0032
✅ Scenario passed!
This output confirms that the test passed, along with the p-value for the statistical test.

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Next Steps

Now that you’ve run your first evaluation, you can start applying SigmaEval to your own Gen AI applications.
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