如何使用应用于多个Pandas数据集列？

import pandas as pd

data = {'col1': [1, 2, 3, 4, 5],
        'col2': [6, 7, 8, 9, 10],
        'col3': [11, 12, 13, 14, 15]}
df = pd.DataFrame(data)

def square(x):
    return x ** 2

df[['col1', 'col2']] = df[['col1', 'col2']].apply(square)

print(df)

import pandas as pd

data = {'col1': [1, 2, 3, 4, 5],
        'col2': [6, 7, 8, 9, 10],
        'col3': [11, 12, 13, 14, 15]}
df = pd.DataFrame(data)

def square(x):
    return x ** 2

df[['col1', 'col2']] = df[['col1', 'col2']].apply(square)

print(df)