pandas的read_csv踩到的坑

Posted 2022-03-20 stephen-qin

read_csv要注意,如果没有设置index_col时,读出来的会在索引上方加上Unnamed:0.可以通过设置index_col来解决这个问题.

import pandas as pd
import numpy as np
df = pd.DataFrame(np.random.randn(5,2) ,columns=[‘a‘, ‘b‘])
df.to_csv(‘2.csv‘)
s= pd.read_csv(‘2.csv‘) #可以看出自动加了一列:Unnamed:0
print(s)
print(s.columns)
print(s.values)
print(type(s.values), s.values.shape)

s= pd.read_csv(‘2.csv‘, index_col=0)
print(s)
 

 

  Unnamed: 0         a         b
0           0  0.917146  1.833755
1           1  1.054247 -2.106368
2           2 -1.418065  3.640767
3           3 -1.840910 -1.098465
4           4 -1.122171  0.061347
Index([‘Unnamed: 0‘, ‘a‘, ‘b‘], dtype=‘object‘)
[[ 0.          0.91714592  1.83375508]
 [ 1.          1.0542468  -2.10636783]
 [ 2.         -1.41806503  3.6407667 ]
 [ 3.         -1.84091041 -1.0984646 ]
 [ 4.         -1.12217057  0.06134697]]
<class ‘numpy.ndarray‘> (5, 3)

a b
0 1.731023 -0.795587
1 -0.500358 0.171487
2 -1.407322 -0.213170
3 -0.226573 0.287079
4 -0.483686 -0.692467