将两列DataFrame旋转为按日期计数的值

import pandas as pd

df1 = pd.DataFrame({'Date': ['2022-01-01', '2022-01-01', '2022-01-02', '2022-01-02'],
                    'Category': ['A', 'B', 'A', 'B'],
                    'Value': [10, 20, 30, 40]})

df2 = pd.DataFrame({'Date': ['2022-01-01', '2022-01-01', '2022-01-02', '2022-01-02'],
                    'Category': ['C', 'D', 'C', 'D'],
                    'Value': [50, 60, 70, 80]})

df = pd.concat([df1, df2])

pivot_df = pd.pivot_table(df, values='Value', index='Date', columns='Category', aggfunc='sum')

print(pivot_df)