juniorScikit-Learn
What is preprocessing in Scikit-Learn?
Updated May 17, 2026
Short answer
Preprocessing prepares raw data into a suitable format for ML models.
Deep explanation
It includes scaling, encoding categorical variables, handling missing values, and normalization using transformers.
Real-world example
Used in finance to normalize income and credit score features.
Common mistakes
- Fitting scaler on full dataset instead of training data only.
Follow-up questions
- Why is scaling important?
- What is normalization vs standardization?