熊貓：讀取列中特殊字符的文件

Question

在我的數據中，某些功能值爲?。我如何將它們替換爲NA？

EDIT

的代碼和輸出是如下：

df = pd.read_csv("cca-census-income.csv", header = None) 

df.replace('?', np.nan, inplace=True) 

df.ix[0,] 

23    Other relative of householder 
24          1700.09 
25           ? 
26           ? 
27           ? 
28    Not in universe under 1 year old 
29           ? 
30           0 

Answer 1

添加參數na_values='?'到read_csv。

樣品：

import pandas as pd 
import io 


temp=u"""Date Time,a 
2010-01-27 16:00:00,? 
2010-01-27 16:10:00,2.2 
2010-01-27 16:30:00,1.7""" 

df = pd.read_csv(io.StringIO(temp),na_values='?') 
print (df) 
      Date Time a 
0 2010-01-27 16:00:00 NaN 
1 2010-01-27 16:10:00 2.2 
2 2010-01-27 16:30:00 1.7 

編輯：

感謝您'shivsn'的建議添加skipinitialspace=True：

temp=u"""Date Time,a 
? , ? 
? ,? 
2010-01-27 16:30:00,1.7""" 

df = pd.read_csv(io.StringIO(temp),na_values=['?', '? '], skipinitialspace =True) 
print (df) 
      Date Time a 
0     NaN NaN 
1     NaN NaN 
2 2010-01-27 16:30:00 1.7 

EDIT1的文件：

它看起來像只是有space前?：

df = pd.read_csv('census-income.data', 
       header = None, 
       na_values=['?'], 
       skipinitialspace =True) 
print (df) 

Answer 2

讀取文件使用replace後：

df.repalce('.?',np.nan,inplace=True,regex=True)