pandas read_csv导入结果错误 [英] Pandas read_csv import results in error

问题描述

我的csv如下(MQM Q.csv):

My csv is as follows (MQM Q.csv):

Date-Time,Value,Grade,Approval,Interpolation Code 
31/08/2012 12:15:00,,41,1,1 
31/08/2012 12:30:00,,41,1,1 
31/08/2012 12:45:00,,41,1,1 
31/08/2012 13:00:00,,41,1,1 
31/08/2012 13:15:00,,41,1,1 
31/08/2012 13:30:00,,41,1,1 
31/08/2012 13:45:00,,41,1,1 
31/08/2012 14:00:00,,41,1,1 
31/08/2012 14:15:00,,41,1,1

前几行没有值"条目，但稍后开始.

The first few lines have no "Value" entries but they start later on.

这是我的代码:

import pandas as pd 
from StringIO import StringIO
Q = pd.read_csv(StringIO("""/cygdrive/c/temp/MQM Q.csv"""), header=0, usecols=["Date-Time", "Value"], parse_dates=True, dayfirst=True, index_col=0)

我收到以下错误:

Traceback (most recent call last):
  File "daily.py", line 4, in <module>
    Q = pd.read_csv(StringIO("""/cygdrive/c/temp/MQM Q.csv"""), header=0, usecols=["Date-Time", "Value"], parse_dates=True, dayfirst=True, index_col=0)
  File "/usr/lib/python2.7/site-packages/pandas-0.14.0-py2.7-cygwin-1.7.30-x86_64.egg/pandas/io/parsers.py", line 443, in parser_f
    return _read(filepath_or_buffer, kwds)
  File "/usr/lib/python2.7/site-packages/pandas-0.14.0-py2.7-cygwin-1.7.30-x86_64.egg/pandas/io/parsers.py", line 228, in _read
    parser = TextFileReader(filepath_or_buffer, **kwds)
  File "/usr/lib/python2.7/site-packages/pandas-0.14.0-py2.7-cygwin-1.7.30-x86_64.egg/pandas/io/parsers.py", line 533, in __init__
    self._make_engine(self.engine)
  File "/usr/lib/python2.7/site-packages/pandas-0.14.0-py2.7-cygwin-1.7.30-x86_64.egg/pandas/io/parsers.py", line 670, in _make_engine
    self._engine = CParserWrapper(self.f, **self.options)
  File "/usr/lib/python2.7/site-packages/pandas-0.14.0-py2.7-cygwin-1.7.30-x86_64.egg/pandas/io/parsers.py", line 1067, in __init__
    col_indices.append(self.names.index(u))
ValueError: 'Value' is not in list

推荐答案

这似乎是csv解析器的错误，首先有效:

This appears to be a bug with the csv parser, firstly this works:

df = pd.read_csv('MQM Q.csv')

这也有效:

df = pd.read_csv('MQM Q.csv', usecols=['Value'])

但是如果我想要Date-Time，它将失败，并显示与您相同的错误消息.

but if I want Date-Time then it fails with the same error message as yours.

所以我注意到它是utf-8编码的，所以我使用notepad ++转换为ANSI并起作用，然后我尝试了没有BOM的utf-8，它也起作用了.

So I noticed it was utf-8 encoded and so I converted using notepad++ to ANSI and it worked, I then tried utf-8 without BOM and it also worked.

然后我将其转换为utf-8(大概现在有一个BOM)，并且失败了，并且错误与以前相同，所以我不认为您现在正在对此进行成像，这看起来像是一个错误.

I then converted it to utf-8 (presumably there is now a BOM) and it failed with the same error as before, so I don't think you are imaging this now and this looks like a bug.

我正在使用python 3.3，pandas 0.14和numpy 1.8.1

I am using python 3.3, pandas 0.14 and numpy 1.8.1

要解决此问题，请执行以下操作:

To get around this do this:

df = pd.read_csv('MQM Q.csv', usecols=[0,1], parse_dates=True, dayfirst=True, index_col=0)

这会将您的索引设置为Date-Time列，该列将正确转换为datetimeindex.

This will set your index to the Date-Time column which will correctly convert to a datetimeindex.

In [40]:

df.index
Out[40]:
<class 'pandas.tseries.index.DatetimeIndex'>
[2012-08-31 12:15:00, ..., 2013-11-28 10:45:00]
Length: 43577, Freq: None, Timezone: None

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