pandas合并数据merge

#!/usr/bin/env python
# _*_ coding: utf-8 _*_

import pandas as pd
import numpy as np

# Test 1
# 定义数据
left = pd.DataFrame({'key': ['K0', 'K1', 'K2', 'K3'],
'A': ['A0', 'A1', 'A2', 'A3'],
'B': ['B0', 'B1', 'B2', 'B3']})
right = pd.DataFrame({'key': ['K0', 'K1', 'K2', 'K3'],
'C': ['C0', 'C1', 'C2', 'C3'],
'D': ['D0', 'D1', 'D2', 'D3']})

print left
print right

# merge合并
res = pd.merge(left, right, on = 'key')
print res

# Test 1 result
A   B key
0  A0  B0  K0
1  A1  B1  K1
2  A2  B2  K2
3  A3  B3  K3
C   D key
0  C0  D0  K0
1  C1  D1  K1
2  C2  D2  K2
3  C3  D3  K3

A   B key   C   D
0  A0  B0  K0  C0  D0
1  A1  B1  K1  C1  D1
2  A2  B2  K2  C2  D2
3  A3  B3  K3  C3  D3

# Test 2
# 定义数据
left = pd.DataFrame({'key1': ['K0', 'K1', 'K2', 'K3'],
'key2': ['K0', 'K1', 'K2', 'K3'],
'A': ['A0', 'A1', 'A2', 'A3'],
'B': ['B0', 'B1', 'B2', 'B3']})
right = pd.DataFrame({'key1': ['K0', 'K1', 'K2', 'K3'],
'key2': ['K0', 'K1', 'K2', 'K4'],
'C': ['C0', 'C1', 'C2', 'C3'],
'D': ['D0', 'D1', 'D2', 'D3']})

print left
print right
# 合并两列, 默认方法是how=inner, 只合并相同的部分, how的取值可以为['left', 'right', 'outer', 'inner']
res = pd.merge(left, right, on = ['key1', 'key2'])
print res

# Test 2 result
A   B key1 key2
0  A0  B0   K0   K0
1  A1  B1   K1   K1
2  A2  B2   K2   K2
3  A3  B3   K3   K3
C   D key1 key2
0  C0  D0   K0   K0
1  C1  D1   K1   K1
2  C2  D2   K2   K2
3  C3  D3   K3   K4
A   B key1 key2   C   D
0  A0  B0   K0   K0  C0  D0
1  A1  B1   K1   K1  C1  D1
2  A2  B2   K2   K2  C2  D2

# Test 3
# 通过indicator表明merge的方式
res = pd.merge(left, right, on = ['key1', 'key2'], how = 'outer', indicator = True)
print res

# 修改indicator的名字
res = pd.merge(left, right, on = ['key1', 'key2'], how = 'outer', indicator = 'indicator')
print res

# Test 3 result
A    B key1 key2    C    D      _merge
0   A0   B0   K0   K0   C0   D0        both
1   A1   B1   K1   K1   C1   D1        both
2   A2   B2   K2   K2   C2   D2        both
3   A3   B3   K3   K3  NaN  NaN   left_only
4  NaN  NaN   K3   K4   C3   D3  right_only

A    B key1 key2    C    D   indicator
0   A0   B0   K0   K0   C0   D0        both
1   A1   B1   K1   K1   C1   D1        both
2   A2   B2   K2   K2   C2   D2        both
3   A3   B3   K3   K3  NaN  NaN   left_only
4  NaN  NaN   K3   K4   C3   D3  right_only

# Test 4
# 定义数据
left = pd.DataFrame({ 'A': ['A0', 'A1', 'A2', 'A3'],
'B': ['B0', 'B1', 'B2', 'B3']},
index = ['K0', 'K1', 'K2', 'K3'])
right = pd.DataFrame({'C': ['C0', 'C1', 'C2', 'C3'],
'D': ['D0', 'D1', 'D2', 'D3']},
index = ['K0', 'K1', 'K2', 'K3'])

print left
print right

# merge数据
res = pd.merge(left, right, left_index = True, right_index = True, how = 'outer')
print res

# Test 4 result
A   B
K0  A0  B0
K1  A1  B1
K2  A2  B2
K3  A3  B3
C   D
K0  C0  D0
K1  C1  D1
K2  C2  D2
K3  C3  D3

A   B   C   D
K0  A0  B0  C0  D0
K1  A1  B1  C1  D1
K2  A2  B2  C2  D2
K3  A3  B3  C3  D3

# Test 5
# 定义数据
left = pd.DataFrame({ 'A': ['A0', 'A1', 'A2', 'A3'],
'B': ['B0', 'B1', 'B2', 'B3']})
right = pd.DataFrame({'A': ['A0', 'A1', 'A2', 'A3'],
'B': ['D0', 'D1', 'D2', 'D3']})

print left
print right

# 区分两个B
res = pd.merge(left, right, on = 'A', how = 'inner', suffixes = ['_left', '_right'])
print res

# Test 5 result
A   B
0  A0  B0
1  A1  B1
2  A2  B2
3  A3  B3
A   B
0  A0  D0
1  A1  D1
2  A2  D2
3  A3  D3
A B_left B_right
0  A0     B0      D0
1  A1     B1      D1
2  A2     B2      D2
3  A3     B3      D3

参考资料