WhyNot is a Python package that provides an experimental sandbox for causal inference and decision making in dynamics. Starting with a suite of dynamic simulations that present realistic technical challenges, WhyNot makes it easy for researchers to develop, test, and benchmark methods for causal inference and reinforcement learning.

What does this look like? The following code generates an observational dataset using an HIV treatment simulator and then runs linear regression to estimate the average treatment effect. These estimates can then subsequently be benchmarked against ground truth.

import numpy as np
import whynot as wn

# Construct causal experiments on sophisticated computer simulations
experiment = wn.hiv.HIVConfounding

# Generate an observational dataset
dataset = experiment.run(num_samples=200, show_progress=True)
# Run your favorite causal inference procedure
estimate = wn.algorithms.ols.estimate_treatment_effect(
    dataset.covariates, dataset.treatments, dataset.outcomes)

# Benchmark the average treatment effect results against the
# ground truth in the dataset
ate = np.mean(dataset.true_effects)
relative_error = np.abs((estimate.ate - ate) / ate)

WhyNot also supports benchmarking and investigation of causal inference tools for heterogenous treatment effects and causal graph discovery.

Beyond causal inference, WhyNot provides simulators and environments to study decision making in dynamics, both in the context of reinforcement learning, as well as from recent perspectives like delayed impact, strategic classification, and performative prediction. The following code uses the same HIV treatment simulator to construct a reinforcement learning environment.

import whynot.gym as gym

env = gym.make("HIV-v0")

observation = env.reset()
for _ in range(100):
    # Random treatment policy
    action = env.action_space.sample()
    observation, reward, done, info = env.step(action)
    if done:
        observation = env.reset()

The code below uses a different environment to study the dynamics of classification when individuals strategically adapt to the decision rule.

import whynot.gym as gym

env = gym.make("Credit-v0")

# A credit dataset collected without strategic adaptation
dataset = env.reset()
for _ in range(100):
    # Random classifier
    # Replace with your favorite machine learning algorithm!
    classifier = env.action_space.sample()

    # New dataset, accounting for strategic response to the classifier
    dataset, loss, done, info = env.step(classifier)
    if done:
        dataset = env.reset()

Documentation

This part of the documentation guides you through all of the library’s usage patterns.

• Why WhyNot?
  • Why Simulations?
  • Dynamical Systems and Causal Inference
  • Related Projects
• Installation
  • Basic Installation Instructions
  • Installing Other Estimators
• Quickstart
  • Basic Concepts - Causal Inference
  • Basic Concepts - Causal Estimators
  • Basic Concepts - Reinforcement Learning
• Simulators
  • Overview
• Usage
  • Causal Inference
  • Causal Graph Discovery
  • Sequential Decision Making
• Examples
  • Causal Inference
  • Decision Making in Dynamics
  • Reinforcement Learning
• Extending Whynot
  • Adding a Simulator
  • Adding an Estimator

API Reference

If you are looking for information on a specific function, class, or method, this part of the documentation is for you.

• API
  • Simulators
  • Dynamics
  • Reinforcement learning
  • Framework
  • Estimators