Python DataFrame에서 행과 열 추가 및 삭제하기

데이터프레임에서 행과 열 추가 및 삭제하기

Python

import pandas as pd
import seaborn as sns
penguins = sns.load_dataset('penguins')
df = penguins.copy()

행 추가 및 삭제

행 추가

pandas에서 행을 추가하는 방법은 크게 3가지가 있다¹.

• df.loc 사용
• df.append() 사용
• concat() 사용

df.loc 사용

index를 명시적으로 지정하여 행을 추가할 수 있다.

df.loc[[len(df.index)-1]]

	species	island	bill_length_mm	bill_depth_mm	flipper_length_mm	body_mass_g	sex
343	Gentoo	Biscoe	49.9	16.1	213.0	5400.0	Male

df.loc[len(df.index)] = ['Adelie', 'Torgersen', 39.2, 19.3, 180.2, 8331, 'Male']
df.loc[len(df.index)-2:]

	species	island	bill_length_mm	bill_depth_mm	flipper_length_mm	body_mass_g	sex
343	Gentoo	Biscoe	49.9	16.1	213.0	5400.0	Male
344	Adelie	Torgersen	39.2	19.3	180.2	8331.0	Male

df.append() 사용

append()² 함수를 사용하여 행을 추가할 수 있다.

df_new = pd.Series(['Adelie', 'Torgersen', 39.2, 19.3, 180.2, 8331, 'Male'], index = df.columns)
df_new

species                 Adelie
island               Torgersen
bill_length_mm            39.2
bill_depth_mm             19.3
flipper_length_mm        180.2
body_mass_g               8331
sex                       Male
dtype: object

df = df.append(df_new, ignore_index=True)
df.tail()

	species	island	bill_length_mm	bill_depth_mm	flipper_length_mm	body_mass_g	sex
340	Gentoo	Biscoe	46.8	14.3	215.0	4850.0	Female
341	Gentoo	Biscoe	50.4	15.7	222.0	5750.0	Male
342	Gentoo	Biscoe	45.2	14.8	212.0	5200.0	Female
343	Gentoo	Biscoe	49.9	16.1	213.0	5400.0	Male
344	Adelie	Torgersen	39.2	19.3	180.2	8331.0	Male

concat() 사용

concat()³ 함수를 이용하여 행을 추가할 수 있다.

df_new = pd.DataFrame([['Adelie', 'Torgersen', 39.2, 19.3, 180.2, 8331, 'Male']], columns = df.columns)
pd.concat([df, df_new], ignore_index = True).tail()

	species	island	bill_length_mm	bill_depth_mm	flipper_length_mm	body_mass_g	sex
340	Gentoo	Biscoe	46.8	14.3	215.0	4850.0	Female
341	Gentoo	Biscoe	50.4	15.7	222.0	5750.0	Male
342	Gentoo	Biscoe	45.2	14.8	212.0	5200.0	Female
343	Gentoo	Biscoe	49.9	16.1	213.0	5400.0	Male
344	Adelie	Torgersen	39.2	19.3	180.2	8331.0	Male

행 삭제

DataFrame에서 데이터를 삭제하는 방법은 drop() 함수를 이용하는 것이다⁴⁵.

DataFrame.drop(labels=None, axis=0, index=None, columns=None, level=None, inplace=False, errors=’raise’)

df.drop(df.index[(1,3), ]).head()

	species	island	bill_length_mm	bill_depth_mm	flipper_length_mm	body_mass_g	sex
0	Adelie	Torgersen	39.1	18.7	181.0	3750.0	Male
2	Adelie	Torgersen	40.3	18.0	195.0	3250.0	Female
4	Adelie	Torgersen	36.7	19.3	193.0	3450.0	Female
5	Adelie	Torgersen	39.3	20.6	190.0	3650.0	Male
6	Adelie	Torgersen	38.9	17.8	181.0	3625.0	Female

df.drop(df.index[100:]).tail()

	species	island	bill_length_mm	bill_depth_mm	flipper_length_mm	body_mass_g	sex
95	Adelie	Dream	40.8	18.9	208.0	4300.0	Male
96	Adelie	Dream	38.1	18.6	190.0	3700.0	Female
97	Adelie	Dream	40.3	18.5	196.0	4350.0	Male
98	Adelie	Dream	33.1	16.1	178.0	2900.0	Female
99	Adelie	Dream	43.2	18.5	192.0	4100.0	Male

df.drop(df[df['species']=='Adelie'].index).head()

	species	island	bill_length_mm	bill_depth_mm	flipper_length_mm	body_mass_g	sex
152	Chinstrap	Dream	46.5	17.9	192.0	3500.0	Female
153	Chinstrap	Dream	50.0	19.5	196.0	3900.0	Male
154	Chinstrap	Dream	51.3	19.2	193.0	3650.0	Male
155	Chinstrap	Dream	45.4	18.7	188.0	3525.0	Female
156	Chinstrap	Dream	52.7	19.8	197.0	3725.0	Male

열 추가 및 삭제

열 추가

import pandas as pd
import seaborn as sns
df = sns.load_dataset("penguins")

df.head()

	species	island	bill_length_mm	bill_depth_mm	flipper_length_mm	body_mass_g	sex
	Adelie	Torgersen	39.1	18.7	181.0	3750.0	Male
	Adelie	Torgersen	39.5	17.4	186.0	3800.0	Female
	Adelie	Torgersen	40.3	18.0	195.0	3250.0	Female
	Adelie	Torgersen	NaN	NaN	NaN	NaN	NaN
	Adelie	Torgersen	36.7	19.3	193.0	3450.0	Female

bill_ratio = df['bill_length_mm']/df['bill_depth_mm']
bill_ratio

0      2.090909
1      2.270115
2      2.238889
3           NaN
4      1.901554
         ...   
339         NaN
340    3.272727
341    3.210191
342    3.054054
343    3.099379
Length: 344, dtype: float64

df['bill_ratio'] = bill_ratio
df.head()

	species	island	bill_length_mm	bill_depth_mm	flipper_length_mm	body_mass_g	sex	bill_ratio
	Adelie	Torgersen	39.1	18.7	181.0	3750.0	Male	2.090909
	Adelie	Torgersen	39.5	17.4	186.0	3800.0	Female	2.270115
	Adelie	Torgersen	40.3	18.0	195.0	3250.0	Female	2.238889
	Adelie	Torgersen	NaN	NaN	NaN	NaN	NaN	NaN
	Adelie	Torgersen	36.7	19.3	193.0	3450.0	Female	1.901554

열 삭제

df.drop(columns = ['sex', 'bill_ratio'], inplace=True)
df.head()

	species	island	bill_length_mm	bill_depth_mm	flipper_length_mm	body_mass_g
	Adelie	Torgersen	39.1	18.7	181.0	3750.0
	Adelie	Torgersen	39.5	17.4	186.0	3800.0
	Adelie	Torgersen	40.3	18.0	195.0	3250.0
	Adelie	Torgersen	NaN	NaN	NaN	NaN
	Adelie	Torgersen	36.7	19.3	193.0	3450.0

원본 데이터에 반영이 필요한 경우 inplace=True 옵션을 적용한다.

참고자료

1. How to add one row in an existing Pandas DataFrame? ↩︎

2. pandas.DataFrame.append ↩︎

3. pandas.concat ↩︎

4. Delete rows/columns from DataFrame using Pandas.drop() ↩︎

5. Drop a list of rows from a Pandas DataFrame ↩︎