Column Transformer
----------------
from sklearn.compose import ColumnTransformer
ct = ColumnTransformer(
transformers=[
("ohe", OneHotEncoder(sparse_output=False), ["city", "gender"])
],
remainder="passthrough" # Keeps all other columns (like age, salary)
).set_output(transform="pandas")
df_processed = ct.fit_transform(df)
--------------------
scaler = StandardScaler().set_output(transform="pandas")
df_scaled = scaler.fit_transform(df)