<ul data-eligibleForWebStory="true">New data scientists often face challenges with real-world messy data compared to clean, toy datasets used in training.Understanding the true context of missing values is crucial for accurate preprocessing.Imputing nulls with zeros in specific cases is more meaningful than using means or medians.Choosing between mean and median imputation depends on data distribution, favoring median for skewed data.Category-wise null imputation can provide more accurate results than overall imputation.Drop_duplicates function may overlook subtle differences and requires thoughtful parameter selection.Scaling data using StandardScaler or MinMaxScaler is essential for models sensitive to feature magnitudes.Feature engineering helps control the explosion of columns in categorical data, improving model performance and explainability.Utilizing feature decomposition algorithms like PCA can manage excessive one-hot encoded columns effectively.Careful consideration is needed when removing outliers to avoid discarding valuable insights within the data.