如何在python DataFrames上进行部分操作

import pandas as pd

data = {'Name': ['John', 'Emma', 'Mike', 'Emily'],
        'Age': [25, 28, 30, 22],
        'City': ['New York', 'London', 'Paris', 'Tokyo']}
df = pd.DataFrame(data)

print(df)

   Name  Age      City
0  John   25  New York
1  Emma   28    London
2  Mike   30     Paris
3  Emily  22     Tokyo

selected_columns = df[['Name', 'Age']]
print(selected_columns)

   Name  Age
0  John   25
1  Emma   28
2  Mike   30
3  Emily  22

selected_rows = df.loc[1:2]
print(selected_rows)

   Name  Age    City
1  Emma   28  London
2  Mike   30   Paris

selected_rows = df[df['Age'] > 25]
print(selected_rows)

   Name  Age    City
1  Emma   28  London
2  Mike   30   Paris

df.loc[0, 'Age'] = 26
print(df)

   Name  Age      City
0  John   26  New York
1  Emma   28    London
2  Mike   30     Paris
3  Emily  22     Tokyo

df['Country'] = ['USA', 'UK', 'France', 'Japan']
print(df)

   Name  Age      City Country
0  John   26  New York     USA
1  Emma   28    London      UK
2  Mike   30     Paris  France
3  Emily  22     Tokyo   Japan