autoclass-lite 0.1.1

A lightweight AutoML library for classification, built from scratch.

autoclass-lite

A lightweight AutoML library for classification, built from scratch using only NumPy. Trains multiple models with cross-validation, ranks them by performance, and returns the best one — all in a single fit() call.

Installation

pip install autoclass-lite

Quick Start

from autoclass_lite import SimpleAutoML, GridAutoML

# Train all models and get a ranked leaderboard
automl = SimpleAutoML()
automl.fit(X_train, y_train)
automl.summary()

# Predict using the best model
predictions = automl.predict(X_test)

# Grid search over hyperparameters
grid = GridAutoML()
grid.fit(X_train, y_train)
grid.summary()

Features

• 4 classifiers implemented from scratch: KNN, Naive Bayes, Logistic Regression, Decision Tree
• K-Fold cross-validation with parallel fold evaluation
• Hyperparameter grid search with memoization cache (dynamic programming)
• Observer-based progress reporting
• Accepts NumPy arrays, Python lists, and Pandas DataFrames

Usage Examples

SimpleAutoML

from autoclass_lite import SimpleAutoML

automl = SimpleAutoML(
    cv_splits=5,        # number of cross-validation folds
    metric="accuracy",  # metric used to rank models
    random_state=42
)
automl.fit(X_train, y_train)
automl.summary()
preds = automl.predict(X_test)

GridAutoML

from autoclass_lite import GridAutoML

param_grid = {
    "logistic_regression": [
        {"learning_rate": 0.01},
        {"learning_rate": 0.1},
    ],
    "knn": [{"k": 3}, {"k": 5}, {"k": 7}],
    "decision_tree": [{"max_depth": 3}, {"max_depth": 5}],
}

grid = GridAutoML(param_grid=param_grid, metric="f1_score")
grid.fit(X_train, y_train)
grid.summary()

Logistic Regression

from autoclass_lite.models.logistic import LogisticRegression

model = LogisticRegression(learning_rate=0.01, n_iterations=1000)
model.fit(X_train, y_train)
predictions = model.predict(X_test)

Metrics

from autoclass_lite.metrics.classification import accuracy, precision, recall, f1_score, evaluate

acc = accuracy(y_true, y_pred)

results = evaluate(y_true, y_pred, metrics=[accuracy, precision, recall, f1_score])

Observer (progress reporting)

from autoclass_lite.automl.observers import ConsoleObserver

automl = SimpleAutoML()
automl.add_observer(ConsoleObserver())
automl.fit(X_train, y_train)

Project Structure

autoclass_lite/
├── __init__.py               # Public API: SimpleAutoML, GridAutoML
├── automl/
│   ├── orchestrator.py       # SimpleAutoML, GridAutoML (Facade pattern)
│   ├── factory.py            # ModelFactory (Factory pattern)
│   └── observers.py          # Observer, ConsoleObserver (Observer pattern)
├── models/
│   ├── base.py               # BaseModel ABC (Strategy + Template Method)
│   ├── logistic.py           # LogisticRegression
│   ├── knn.py                # KNNClassifier
│   ├── naive_bayes.py        # GaussianNaiveBayes
│   └── tree.py               # DecisionTreeClassifier (recursive)
├── cv/
│   ├── splitter.py           # KFoldSplitter
│   └── validator.py          # CrossValidator (ThreadPoolExecutor)
└── metrics/
    └── classification.py     # Pure functions + evaluate() HOF
tests/                        # pytest test suite
pyproject.toml
README.md

---

Learning Outcomes

1. Object-Oriented Programming (OOP)

• Encapsulation: All internal state uses private attributes (_weights, _biases, _cache, etc.). Users interact only through the public API.
• Abstract Base Class: BaseModel in autoclass_lite/models/base.py defines the interface all classifiers must implement.
• Inheritance: KNNClassifier, GaussianNaiveBayes, LogisticRegression, DecisionTreeClassifier all extend BaseModel. GridAutoML extends SimpleAutoML.
• Polymorphism: CrossValidator calls .fit() and .predict() on any BaseModel subclass without knowing its concrete type.

2. Functional Programming

• Pure functions: accuracy, precision, recall, f1_score in autoclass_lite/metrics/classification.py take arrays and return a value with no side effects.
• Higher-order function: evaluate(y_true, y_pred, metrics: list) takes a list of metric functions and applies them, returning a results dict.
• Lambdas as data: KNNClassifier._DISTANCES is a class-level dict mapping distance names to lambda functions, selected at runtime.

3. Concurrency

CrossValidator in autoclass_lite/cv/validator.py uses ThreadPoolExecutor to evaluate all K folds in parallel. Each fold gets a copy.deepcopy of the model to ensure thread safety.

with ThreadPoolExecutor() as executor:
    futures = [executor.submit(self._evaluate_fold, ...) for fold in folds]

4. Recursion / Dynamic Programming

• Recursion: DecisionTreeClassifier in autoclass_lite/models/tree.py uses _grow_tree() to recursively split nodes and _traverse() to recursively walk the tree during prediction.
• Dynamic Programming (Memoization): GridAutoML in autoclass_lite/automl/orchestrator.py maintains a _cache dict. Every (model_name, params) combination is evaluated at most once — repeated configurations are looked up from cache instead of re-running cross-validation.

cache_key = (name, frozenset(params.items()))
if cache_key in self._cache:
    scores = self._cache[cache_key]
else:
    scores = validator.validate(model, X, y)
    self._cache[cache_key] = scores

5. SOLID Principles

• Single Responsibility: Each class does exactly one thing. KFoldSplitter only splits indices. CrossValidator only runs folds. ModelFactory only creates models.
• Open/Closed: New models can be added by extending BaseModel and registering in ModelFactory without touching existing code. SimpleAutoML.DEFAULT_CONFIGS allows adding new default configurations without modifying fit().
• Liskov Substitution: Any BaseModel subclass can replace another anywhere in the system.
• Interface Segregation: BaseModel only requires fit and predict. Optional get_params has a default implementation in the base class.
• Dependency Inversion: CrossValidator depends on BaseModel (abstraction), not any concrete classifier.

6. Architectural & Design Patterns

Architecture: Layered pipeline — models → cross-validation → metrics → AutoML orchestration. Each layer depends only on the layer below it.

Factory Pattern — autoclass_lite/automl/factory.py

ModelFactory.create(name, **kwargs) instantiates any registered model by name. Adding a new model requires only one line in the registry dict.

Strategy Pattern — autoclass_lite/models/base.py, autoclass_lite/models/knn.py

• BaseModel defines the classifier interface; each model is a concrete strategy swappable at runtime by ModelFactory.
• KNNClassifier._DISTANCES selects the distance function at construction time — euclidean or manhattan — without any if/else in the prediction loop.

Observer Pattern — autoclass_lite/automl/observers.py

SimpleAutoML notifies all registered observers on fit_start, model_done, and fit_done events without coupling to any specific logger or UI.

Template Method Pattern — autoclass_lite/models/base.py

BaseModel.fit_predict() defines the skeleton (fit then predict). Subclasses implement the steps; the sequence is inherited and never duplicated.

Facade Pattern — autoclass_lite/automl/orchestrator.py

SimpleAutoML exposes a single fit() / predict() / summary() interface that internally coordinates model creation, cross-validation, and ranking.