使用 .loc 與 .iloc 的切片與子集
使用 pandas 進行資料操作
Richie Cotton
Data Evangelist at DataCamp
列表切片
breeds = ["Labrador", "Poodle",
"Chow Chow", "Schnauzer",
"Labrador", "Chihuahua",
"St. Bernard"]
['Labrador',
'Poodle',
'Chow Chow',
'Schnauzer',
'Labrador',
'Chihuahua',
'St. Bernard']
breeds[2:5]
['Chow Chow', 'Schnauzer', 'Labrador']
breeds[:3]
['Labrador', 'Poodle', 'Chow Chow']
breeds[:]
['Labrador','Poodle','Chow Chow','Schnauzer',
'Labrador','Chihuahua','St. Bernard']
切片前先排序索引
dogs_srt = dogs.set_index(["breed", "color"]).sort_index()
print(dogs_srt)
name height_cm weight_kg
breed color
Chihuahua Tan Stella 18 2
Chow Chow Brown Lucy 46 22
Labrador Black Max 59 29
Brown Bella 56 25
Poodle Black Charlie 43 23
Schnauzer Grey Cooper 49 17
St. Bernard White Bernie 77 74
切片外層索引層級
dogs_srt.loc["Chow Chow":"Poodle"]
name height_cm weight_kg
breed color
Chow Chow Brown Lucy 46 22
Labrador Black Max 59 29
Brown Bella 56 25
Poodle Black Charlie 43 23
最後一個值 "Poodle" 會被包含
完整資料集
name height_cm weight_kg
breed color
Chihuahua Tan Stella 18 2
Chow Chow Brown Lucy 46 22
Labrador Black Max 59 29
Brown Bella 56 25
Poodle Black Charlie 43 23
Schnauzer Grey Cooper 49 17
St. Bernard White Bernie 77 74
錯誤切片內層索引
dogs_srt.loc["Tan":"Grey"]
Empty DataFrame
Columns: [name, height_cm, weight_kg]
Index: []
完整資料集
name height_cm weight_kg
breed color
Chihuahua Tan Stella 18 2
Chow Chow Brown Lucy 46 22
Labrador Black Max 59 29
Brown Bella 56 25
Poodle Black Charlie 43 23
Schnauzer Grey Cooper 49 17
St. Bernard White Bernie 77 74
正確切片內層索引
dogs_srt.loc[
("Labrador", "Brown"):("Schnauzer", "Grey")]
name height_cm weight_kg
breed color
Labrador Brown Bella 56 25
Poodle Black Charlie 43 23
Schnauzer Grey Cooper 49 17
完整資料集
name height_cm weight_kg
breed color
Chihuahua Tan Stella 18 2
Chow Chow Brown Lucy 46 22
Labrador Black Max 59 29
Brown Bella 56 25
Poodle Black Charlie 43 23
Schnauzer Grey Cooper 49 17
St. Bernard White Bernie 77 74
欄切片
dogs_srt.loc[:, "name":"height_cm"]
name height_cm
breed color
Chihuahua Tan Stella 18
Chow Chow Brown Lucy 46
Labrador Black Max 59
Brown Bella 56
Poodle Black Charlie 43
Schnauzer Grey Cooper 49
St. Bernard White Bernie 77
完整資料集
name height_cm weight_kg
breed color
Chihuahua Tan Stella 18 2
Chow Chow Brown Lucy 46 22
Labrador Black Max 59 29
Brown Bella 56 25
Poodle Black Charlie 43 23
Schnauzer Grey Cooper 49 17
St. Bernard White Bernie 77 74
雙重切片
dogs_srt.loc[
("Labrador", "Brown"):("Schnauzer", "Grey"),
"name":"height_cm"]
name height_cm
breed color
Labrador Brown Bella 56
Poodle Black Charlie 43
Schanuzer Grey Cooper 49
完整資料集
name height_cm weight_kg
breed color
Chihuahua Tan Stella 18 2
Chow Chow Brown Lucy 46 22
Labrador Black Max 59 29
Brown Bella 56 25
Poodle Black Charlie 43 23
Schnauzer Grey Cooper 49 17
St. Bernard White Bernie 77 74
Dog days（狗狗生日）
dogs = dogs.set_index("date_of_birth").sort_index()
print(dogs)
name breed color height_cm weight_kg
date_of_birth
2011-12-11 Cooper Schanuzer Grey 49 17
2013-07-01 Bella Labrador Brown 56 25
2014-08-25 Lucy Chow Chow Brown 46 22
2015-04-20 Stella Chihuahua Tan 18 2
2016-09-16 Charlie Poodle Black 43 23
2017-01-20 Max Labrador Black 59 29
2018-02-27 Bernie St. Bernard White 77 74
用日期切片
# 取得 2014-08-25 到 2016-09-16 出生的狗
dogs.loc["2014-08-25":"2016-09-16"]
name breed color height_cm weight_kg
date_of_birth
2014-08-25 Lucy Chow Chow Brown 46 22
2015-04-20 Stella Chihuahua Tan 18 2
2016-09-16 Charlie Poodle Black 43 23
用部分日期切片
# 取得 2014-01-01 到 2016-12-31 出生的狗
dogs.loc["2014":"2016"]
name breed color height_cm weight_kg
date_of_birth
2014-08-25 Lucy Chow Chow Brown 46 22
2015-04-20 Stella Chihuahua Tan 18 2
2016-09-16 Charlie Poodle Black 43 23
以列／欄編號取子集
print(dogs.iloc[2:5, 1:4])
breed color height_cm
2 Chow Chow Brown 46
3 Schnauzer Grey 49
4 Labrador Black 59
完整資料集
name breed color height_cm weight_kg
0 Bella Labrador Brown 56 25
1 Charlie Poodle Black 43 23
2 Lucy Chow Chow Brown 46 22
3 Cooper Schnauzer Grey 49 17
4 Max Labrador Black 59 29
5 Stella Chihuahua Tan 18 2
6 Bernie St. Bernard White 77 74
一起來練習吧！
使用 pandas 進行資料操作
