代码
import pandas as pd
import numpy as np
left=pd.DataFrame({'key':['K0','K1','K2','K3'],
'A':['A0','A1','A3','A3'],
'B':['B0','B1','B2','B3'],})
right=pd.DataFrame({'key':['K0','K1','K2','K3'],
'C':['C0','C1','C3','C3'],
'D':['D0','D1','D2','D3'],})
print('-1-')
print(left)
print(right)
res = pd.merge(left,right,on='key')
print(res)
left=pd.DataFrame({'key1':['K0','K0','K1','K2'],
'key2':['K0','K1','K0','K1'],
'A':['A0','A1','A3','A3'],
'B':['B0','B1','B2','B3'],})
right=pd.DataFrame({'key1':['K0','K1','K1','K2'],
'key2':['K0','K0','K0','K0'],
'C':['C0','C1','C3','C3'],
'D':['D0','D1','D2','D3'],})
print('-2-')
res = pd.merge(left,right,on=['key1','key2'])
print(left)
print(right)
print(res)
# default
print('-3-')
res = pd.merge(left,right,on=['key1','key2'],how='inner')
print(left)
print(right)
print(res)
print('-4-')
res = pd.merge(left,right,on=['key1','key2'],how='outer')
print(left)
print(right)
print(res)
print('-5-')
res = pd.merge(left,right,on=['key1','key2'],how='right')
print(left)
print(right)
print(res)
print('-6-')
res = pd.merge(left,right,on=['key1','key2'],how='left')
print(left)
print(right)
print(res)
print('-7-')
df1 = pd.DataFrame({'col1':[0,1],'col_left':['a','b']})
df2 = pd.DataFrame({'col1':[1,2,2],'col_right':[2,2,2]})
print(df1)
print(df2)
res = pd.merge(df1,df2,on='col1',how='outer',indicator=True)
print(res)
res = pd.merge(df1,df2,on='col1',how='outer',indicator=True)
print(res)
res = pd.merge(df1,df2,on='col1',how='outer',indicator='indicator_column')
print(res)
df1 = pd.DataFrame({'A':['A0','A1','A2'],
'B':['B0','B1','B2']},
index=['K0','K1','K2'])
df2 = pd.DataFrame({'C':['C0','C1','C2'],
'D':['D0','D1','D2']},
index=['K0','K1','K2'])
print(df1)
print(df2)
print('-8-')
res=pd.merge(left,right,left_index=True,right_index=True,how='outer')
print(res)
print('-9-')
res=pd.merge(left,right,left_index=True,right_index=True,how='inner')
print(res)
boys = pd.DataFrame({'k':['K0','K1','K2'],'age':[1,2,3]})
girls = pd.DataFrame({'k':['K0','K0','K3'],'age':[4,5,6]})
print('-10-')
print(boys)
print(girls)
res = pd.merge(boys, girls, on='k', suffixes=['_boy','_girl'],how='inner')
print(res)
res = pd.merge(boys, girls, on='k', suffixes=['_boy','_girl'],how='outer')
print(res)
输出
-1-
key A B
0 K0 A0 B0
1 K1 A1 B1
2 K2 A3 B2
3 K3 A3 B3
key C D
0 K0 C0 D0
1 K1 C1 D1
2 K2 C3 D2
3 K3 C3 D3
key A B C D
0 K0 A0 B0 C0 D0
1 K1 A1 B1 C1 D1
2 K2 A3 B2 C3 D2
3 K3 A3 B3 C3 D3
-2-
key1 key2 A B
0 K0 K0 A0 B0
1 K0 K1 A1 B1
2 K1 K0 A3 B2
3 K2 K1 A3 B3
key1 key2 C D
0 K0 K0 C0 D0
1 K1 K0 C1 D1
2 K1 K0 C3 D2
3 K2 K0 C3 D3
key1 key2 A B C D
0 K0 K0 A0 B0 C0 D0
1 K1 K0 A3 B2 C1 D1
2 K1 K0 A3 B2 C3 D2
-3-
key1 key2 A B
0 K0 K0 A0 B0
1 K0 K1 A1 B1
2 K1 K0 A3 B2
3 K2 K1 A3 B3
key1 key2 C D
0 K0 K0 C0 D0
1 K1 K0 C1 D1
2 K1 K0 C3 D2
3 K2 K0 C3 D3
key1 key2 A B C D
0 K0 K0 A0 B0 C0 D0
1 K1 K0 A3 B2 C1 D1
2 K1 K0 A3 B2 C3 D2
-4-
key1 key2 A B
0 K0 K0 A0 B0
1 K0 K1 A1 B1
2 K1 K0 A3 B2
3 K2 K1 A3 B3
key1 key2 C D
0 K0 K0 C0 D0
1 K1 K0 C1 D1
2 K1 K0 C3 D2
3 K2 K0 C3 D3
key1 key2 A B C D
0 K0 K0 A0 B0 C0 D0
1 K0 K1 A1 B1 NaN NaN
2 K1 K0 A3 B2 C1 D1
3 K1 K0 A3 B2 C3 D2
4 K2 K1 A3 B3 NaN NaN
5 K2 K0 NaN NaN C3 D3
-5-
key1 key2 A B
0 K0 K0 A0 B0
1 K0 K1 A1 B1
2 K1 K0 A3 B2
3 K2 K1 A3 B3
key1 key2 C D
0 K0 K0 C0 D0
1 K1 K0 C1 D1
2 K1 K0 C3 D2
3 K2 K0 C3 D3
key1 key2 A B C D
0 K0 K0 A0 B0 C0 D0
1 K1 K0 A3 B2 C1 D1
2 K1 K0 A3 B2 C3 D2
3 K2 K0 NaN NaN C3 D3
-6-
key1 key2 A B
0 K0 K0 A0 B0
1 K0 K1 A1 B1
2 K1 K0 A3 B2
3 K2 K1 A3 B3
key1 key2 C D
0 K0 K0 C0 D0
1 K1 K0 C1 D1
2 K1 K0 C3 D2
3 K2 K0 C3 D3
key1 key2 A B C D
0 K0 K0 A0 B0 C0 D0
1 K0 K1 A1 B1 NaN NaN
2 K1 K0 A3 B2 C1 D1
3 K1 K0 A3 B2 C3 D2
4 K2 K1 A3 B3 NaN NaN
-7-
col1 col_left
0 0 a
1 1 b
col1 col_right
0 1 2
1 2 2
2 2 2
col1 col_left col_right _merge
0 0 a NaN left_only
1 1 b 2.0 both
2 2 NaN 2.0 right_only
3 2 NaN 2.0 right_only
col1 col_left col_right _merge
0 0 a NaN left_only
1 1 b 2.0 both
2 2 NaN 2.0 right_only
3 2 NaN 2.0 right_only
col1 col_left col_right indicator_column
0 0 a NaN left_only
1 1 b 2.0 both
2 2 NaN 2.0 right_only
3 2 NaN 2.0 right_only
A B
K0 A0 B0
K1 A1 B1
K2 A2 B2
C D
K0 C0 D0
K1 C1 D1
K2 C2 D2
-8-
key1_x key2_x A B key1_y key2_y C D
0 K0 K0 A0 B0 K0 K0 C0 D0
1 K0 K1 A1 B1 K1 K0 C1 D1
2 K1 K0 A3 B2 K1 K0 C3 D2
3 K2 K1 A3 B3 K2 K0 C3 D3
-9-
key1_x key2_x A B key1_y key2_y C D
0 K0 K0 A0 B0 K0 K0 C0 D0
1 K0 K1 A1 B1 K1 K0 C1 D1
2 K1 K0 A3 B2 K1 K0 C3 D2
3 K2 K1 A3 B3 K2 K0 C3 D3
-10-
k age
0 K0 1
1 K1 2
2 K2 3
k age
0 K0 4
1 K0 5
2 K3 6
k age_boy age_girl
0 K0 1 4
1 K0 1 5
k age_boy age_girl
0 K0 1.0 4.0
1 K0 1.0 5.0
2 K1 2.0 NaN
3 K2 3.0 NaN
4 K3 NaN 6.0