数据合并 concat

import numpy as np
import pandas as pd

NumPy的concat

arr1 = np.random.randint(0, 10, (3, 4))
arr2 = np.random.randint(0, 10, (3, 4))

print(arr1)
print(arr2)

[[0 2 5 2]
 [6 3 1 0]
 [4 2 6 9]]
[[2 5 4 1]
 [5 5 4 4]
 [4 3 3 3]]

np.concatenate([arr1, arr2])

array([[0, 2, 5, 2],
       [6, 3, 1, 0],
       [4, 2, 6, 9],
       [2, 5, 4, 1],
       [5, 5, 4, 4],
       [4, 3, 3, 3]])

np.concatenate([arr1, arr2], axis=1)

array([[0, 2, 5, 2, 2, 5, 4, 1],
       [6, 3, 1, 0, 5, 5, 4, 4],
       [4, 2, 6, 9, 4, 3, 3, 3]])

Series上的concat

index 没有重复的情况

ser_obj1 = pd.Series(np.random.randint(0, 10, 5), index=range(0,5))
ser_obj2 = pd.Series(np.random.randint(0, 10, 4), index=range(5,9))
ser_obj3 = pd.Series(np.random.randint(0, 10, 3), index=range(9,12))

print(ser_obj1)
print(ser_obj2)
print(ser_obj3)

0    4
1    3
2    0
3    5
4    0
dtype: int32
5    1
6    1
7    4
8    8
dtype: int32
9     8
10    9
11    6
dtype: int32

pd.concat([ser_obj1, ser_obj2, ser_obj3])

0     4
1     3
2     0
3     5
4     0
5     1
6     1
7     4
8     8
9     8
10    9
11    6
dtype: int32

pd.concat([ser_obj1, ser_obj2, ser_obj3], axis=1)

Paste_Image.png

index 有重复的情况

ser_obj1 = pd.Series(np.random.randint(0, 10, 5), index=range(5))
ser_obj2 = pd.Series(np.random.randint(0, 10, 4), index=range(4))
ser_obj3 = pd.Series(np.random.randint(0, 10, 3), index=range(3))

print(ser_obj1)
print(ser_obj2)
print(ser_obj3)

0    1
1    4
2    7
3    6
4    0
dtype: int32
0    6
1    3
2    6
3    6
dtype: int32
0    2
1    0
2    0
dtype: int32

pd.concat([ser_obj1, ser_obj2, ser_obj3])

0    1
1    4
2    7
3    6
4    0
0    6
1    3
2    6
3    6
0    2
1    0
2    0
dtype: int32

pd.concat([ser_obj1, ser_obj2, ser_obj3], axis=1, join='inner')

Paste_Image.png

DataFrame上的concat

df_obj1 = pd.DataFrame(np.random.randint(0, 10, (3, 2)), index=['a', 'b', 'c'],
                       columns=['A', 'B'])
df_obj2 = pd.DataFrame(np.random.randint(0, 10, (2, 2)), index=['a', 'b'],
                       columns=['C', 'D'])
print(df_obj1)
print(df_obj2)

   A  B
a  7  2
b  4  7
c  1  3
   C  D
a  8  3
b  5  8

pd.concat([df_obj1, df_obj2])

Paste_Image.png

pd.concat([df_obj1, df_obj2], axis=1)

Paste_Image.png