from sklearn.preprocessing import StandardScaler
import pandas as pd

data = {'Age': [20, 25, 30, 35, 40],
 'Salary': [20000, 25000, 30000, 35000, 40000]}

df = pd.DataFrame(data)

scaler = StandardScaler()

df[['Age_scaled', 'Salary_scaled']] = scaler.fit_transform(df[['Age', 'Salary']])
print(df)