from sklearn.model_selection import train_test_split
df=df.dropna()
X=df.drop(['4-year resale value'], axis=1)
y=df[['4-year resale value']]
X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.25, random_state=1)

from sklearn import preprocessing
import numpy as np
scaler = preprocessing.StandardScaler().fit(X_train)
X_scaled=scaler.transform(X_train)

X_test_sc=scaler.transform(X_test)