如何根据设置的开始日期和结束日期之间的时间间隔来扩展具有额外行的DataFrame？

import pandas as pd
from datetime import datetime, timedelta

df = pd.DataFrame(columns=['日期', '数值'])
start_date = datetime(2022, 1, 1)
end_date = datetime(2022, 1, 10)

delta = end_date - start_date
for i in range(delta.days + 1):
    date = start_date + timedelta(days=i)
    df = df.append({'日期': date, '数值': 0}, ignore_index=True)

df['数值'] = df['数值'].fillna(0)  # 填充缺失值为0
df['数值'] = df['数值'].astype(int)  # 将数值列转换为整数类型
mean_value = df['数值'].mean()  # 计算数值列的平均值