python - Groupby、Shift 和 Sum

Question

我有以下数据框:

product    Week_Number       Sales
1               1              10
2               1              15
1               2              20

我想按产品和周数分组，并创建一个包含该产品下周销售额的列:

product    Week_Number       Sales       next_week
1               1              10            20      
2               1              15             0
1               2              20             0

Answer 1

使用DataFrame.sort_values与 DataFrameGroupBy.shift :

#if not sure if sorted per 2 columns
df = df.sort_values(['product','Week_Number'])

#pandas 0.24+
df['next_week'] = df.groupby('product')['Sales'].shift(-1, fill_value=0)
#pandas below
#df['next_week'] = df.groupby('product')['Sales'].shift(-1).fillna(0, downcast='int')
print (df)
   product  Week_Number  Sales  next_week
0        1            1     10         20
1        2            1     15          0
2        1            2     20          0

如果可能重复并需要先在真实数据中聚合sum:

df = df.groupby(['product','Week_Number'], as_index=False)['Sales'].sum()
df['next_week'] = df.groupby('product')['Sales'].shift(-1).fillna(0, downcast='int')
print (df)
   product  Week_Number  Sales  next_week
0        1            1     10         20
1        1            2     20          0
2        2            1     15          0