如何创建一个新的数据帧`df2‘，它汇总了数据帧`df1’的行数，但以DateTime为条件

import pandas as pd

df1 = pd.DataFrame({'DateTime': ['2022-01-01', '2022-01-02', '2022-01-03'],
                    'Value': [10, 20, 30]})

df1['DateTime'] = pd.to_datetime(df1['DateTime'])

condition = df1['DateTime'] > '2022-01-01'  # 设置DateTime条件
df2 = df1[condition]  # 筛选出满足条件的行
row_count = len(df2)  # 计算行数

print("满足条件的行数：", row_count)
print(df2)