处理多级索引
使用 pandas 重塑数据
Maria Eugenia Inzaugarat
Instructor
复习
- 对 DataFrame 和 Series 进行堆叠与取消堆叠
- 通过名称或编号选择要堆叠/取消堆叠的层级
- 组合取消堆叠与堆叠以重新排列层级
重排多级索引
- 交换层级
- 同时对多个层级进行堆叠与取消堆叠
交换层级
交换层级
cars
2019 2020
price Golf VW 25 26
sold Golf VW 68 72
price Passat VW 31 32
sold Passat VW 72 73
price A-class Mercedes 41 42
sold A-class Mercedes 68 69
price C-class Mercedes 32 33
sold C-class Mercedes 75 74
交换层级
cars
2019 2020
price Golf VW 25 26
sold Golf VW 68 72
price Passat VW 31 32
sold Passat VW 72 73
price A-class Mercedes 41 42
sold A-class Mercedes 68 69
price C-class Mercedes 32 33
sold C-class Mercedes 75 74
cars.swaplevel(0, 2)
2019 2020
VW Golf price 25 26
sold 68 72
Passat price 31 32
sold 72 73
Mercedes A-class price 41 42
sold 68 69
C-class price 32 33
sold 75 74
交换层级并取消堆叠
cars
2019 2020
price Golf VW 25 26
sold Golf VW 68 72
price Passat VW 31 32
sold Passat VW 72 73
price A-class Mercedes 41 42
sold A-class Mercedes 68 69
price C-class Mercedes 32 33
sold C-class Mercedes 75 74
cars.swaplevel(0, 2).unstack()
2019 2020
price sold price sold
Mercedes A-class 41 68 42 69
C-class 32 75 33 74
VW Golf 25 68 26 72
Passat 31 72 32 73
交换层级并取消堆叠
cars
2019 2020
price Golf VW 25 26
sold Golf VW 68 72
price Passat VW 31 32
sold Passat VW 72 73
price A-class Mercedes 41 42
sold A-class Mercedes 68 69
price C-class Mercedes 32 33
sold C-class Mercedes 75 74
cars.unstack()
Mercedes VW Mercedes VW
2019 2019 2020 2020
price A-class 41.0 NaN 42.0 NaN
C-class 32.0 NaN 33.0 NaN
Golf NaN 25.0 NaN 26.0
Passat NaN 31.0 NaN 32.0
sold A-class 68.0 NaN 69.0 NaN
C-class 75.0 NaN 74.0 NaN
Golf NaN 68.0 NaN 72.0
Passat NaN 72.0 NaN 73.0
交换层级并取消堆叠
cars
2019 2020
price Golf VW 25 26
sold Golf VW 68 72
price Passat VW 31 32
sold Passat VW 72 73
price A-class Mercedes 41 42
sold A-class Mercedes 68 69
price C-class Mercedes 32 33
sold C-class Mercedes 75 74
cars.unstack().swaplevel(0, 1, axis=1)
2019 2020
Mercedes VW Mercedes VW
price A-class 41.0 NaN 42.0 NaN
C-class 32.0 NaN 33.0 NaN
Golf NaN 25.0 NaN 26.0
Passat NaN 31.0 NaN 32.0
sold A-class 68.0 NaN 69.0 NaN
C-class 75.0 NaN 74.0 NaN
Golf NaN 68.0 NaN 72.0
Passat NaN 72.0 NaN 73.0
交换层级并堆叠
cars
2019 2020
price Golf VW 25 26
sold Golf VW 68 72
price Passat VW 31 32
sold Passat VW 72 73
price A-class Mercedes 41 42
sold A-class Mercedes 68 69
price C-class Mercedes 32 33
sold C-class Mercedes 75 74
cars.stack()
price Golf VW 2019 25
2020 26
sold Golf VW 2019 68
2020 72
price Passat VW 2019 31
2020 32
sold Passat VW 2019 72
2020 73
price A-class Mercedes 2019 41
2020 42
sold A-class Mercedes 2019 68
2020 69
交换层级并堆叠
cars
2019 2020
price Golf VW 25 26
sold Golf VW 68 72
price Passat VW 31 32
sold Passat VW 72 73
price A-class Mercedes 41 42
sold A-class Mercedes 68 69
price C-class Mercedes 32 33
sold C-class Mercedes 75 74
cars.stack().swaplevel(0, 2)
VW Golf price 2019 25
2020 26
sold 2019 68
2020 72
Passat price 2019 31
2020 32
sold 2019 72
2020 73
Mercedes A-class price 2019 41
2020 42
sold 2019 68
2020 69
多级索引
取消多个层级的堆叠
cars
year 2019 2020
brand model feature
VW Golf price 25 26
sold 68 72
Passat price 31 32
sold 72 73
Mercedes A-class price 41 42
sold 68 69
C-class price 32 33
sold 75 74
按编号取消堆叠
cars.unstack(level=[0, 1])
year 2019 2020
brand VW Mercedes VW Mercedes
model Golf Passat A-class C-class Golf Passat A-class C-class
feature
price 25 31 41 32 26 32 42 33
sold 68 72 68 75 72 73 69 74
按名称取消堆叠
cars.unstack(level=['brand', 'model'])
year 2019 2020
brand VW Mercedes VW Mercedes
model Golf Passat A-class C-class Golf Passat A-class C-class
feature
price 25 31 41 32 26 32 42 33
sold 68 72 68 75 72 73 69 74
堆叠多个层级
cars_unstacked
year 2019 2020
brand VW Mercedes VW Mercedes
model Golf Passat A-class C-class Golf Passat A-class C-class
feature
price 25 31 41 32 26 32 42 33
sold 68 72 68 75 72 73 69 74
按名称或编号堆叠
cars_unstacked.stack(level=[0, 1])
model A-class C-class Golf Passat
feature year brand
price 2019 Mercedes 41.0 32.0 NaN NaN
VW NaN NaN 25.0 31.0
2020 Mercedes 42.0 33.0 NaN NaN
VW NaN NaN 26.0 32.0
sold 2019 Mercedes 68.0 75.0 NaN NaN
VW NaN NaN 68.0 72.0
2020 Mercedes 69.0 74.0 NaN NaN
VW NaN NaN 72.0 73.0
cars_unstacked.stack(level=['year', 'brand'])
model A-class C-class Golf Passat
feature year brand
price 2019 Mercedes 41.0 32.0 NaN NaN
VW NaN NaN 25.0 31.0
2020 Mercedes 42.0 33.0 NaN NaN
VW NaN NaN 26.0 32.0
sold 2019 Mercedes 68.0 75.0 NaN NaN
VW NaN NaN 68.0 72.0
2020 Mercedes 69.0 74.0 NaN NaN
VW NaN NaN 72.0 73.0
让我们来练习！
使用 pandas 重塑数据
