python - 接下来 n 行的更复杂的滚动总和

Question

我有以下数据框:

print(df)
  day     month    year    quantity    
   6       04      2018       10
   8       04      2018        8
  12       04      2018        8

我想创建一个列，即接下来的“n”天的“数量”的总和，如下所示:

n = 2

print(df1)
  day     month    year    quantity  final_quantity    
   6       04      2018       10     10 + 0 + 8 = 18
   8       04      2018        8      8 + 0 + 0 = 8
  12       04      2018        8      8 + 0 + 0 = 8

具体来说，如果产品在接下来的“n”天内未售出，则求和0。我尝试从 Pandas 中滚动求和，但似乎不适用于不同的列:

n = 2
df.quantity[::-1].rolling(n + 1, min_periods=1).sum()[::-1]

Answer 1

您可以使用列表理解:

import pandas as pd

df['DateTime'] = pd.to_datetime(df[['year', 'month', 'day']])

df['final_quantity'] = [df.loc[df['DateTime'].between(d, d+pd.Timedelta(days=2)), 'quantity'].sum() \
                        for d in df['DateTime']]

print(df)

#    day  month  year  quantity   DateTime  final_quantity
# 0    6      4  2018        10 2018-04-06              18
# 1    8      4  2018         8 2018-04-08               8
# 2   12      4  2018         8 2018-04-12               8