The most popular library for traditional machine learning algorithms.
Scikit-learn is the gold standard for general-purpose machine learning in Python. It offers a vast collection of tools for data analysis and modeling, all within a clean, consistent, and well-documented framework. Its power lies in its simplicity and unified API. The core pattern in Scikit-learn is `estimator.fit(data, labels)` to train a model and `estimator.predict(new_data)` to make predictions. This consistent interface applies across all algorithms, making it incredibly easy to experiment with different models. Whether you are using a Linear Regression, a Decision Tree, or a Support Vector Machine, the basic workflow remains the same. Scikit-learn provides a wide range of supervised and unsupervised learning algorithms. For supervised learning, it covers classification (e.g., Logistic Regression, K-Nearest Neighbors) and regression (e.g., Linear Regression, Ridge Regression). For unsupervised learning, it includes algorithms for clustering (e.g., K-Means, DBSCAN), dimensionality reduction (e.g., PCA, t-SNE), and anomaly detection. Beyond the algorithms themselves, Scikit-learn offers a comprehensive suite of tools for the entire ML pipeline. It has functions for data preprocessing (like scaling and encoding), model selection (like train-test split and cross-validation), and model evaluation (like calculating accuracy, precision, and recall). This end-to-end functionality makes Scikit-learn an indispensable tool for nearly any machine learning project that doesn't require the complexity of deep learning frameworks.