Python Pandas read_csv 导入导致错误
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Pandas read_csv import results in error
提问by Sid Kwakkel
My csv is as follows (MQM Q.csv):
我的csv如下（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
The first few lines have no "Value" entries but they start later on.
前几行没有“值”条目，但它们稍后开始。
Here is my code:
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)
I get the following error:
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
采纳答案by EdChum
This appears to be a bug with the csv parser, firstly this works:
这似乎是 csv 解析器的一个错误，首先这是有效的：
df = pd.read_csv('MQM Q.csv')
also this works:
这也有效：
df = pd.read_csv('MQM Q.csv', usecols=['Value'])
but if I want Date-Timethen it fails with the same error message as yours.
但是如果我想要，Date-Time它会失败并显示与您相同的错误消息。
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.
所以我注意到它是 utf-8 编码的，所以我使用 notepad++ 转换为 ANSI 并且它有效，然后我尝试了没有 BOM 的 utf-8 并且它也有效。
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.
然后我将它转换为 utf-8（大概现在有一个 BOM）并且它失败了，并出现了与以前相同的错误，所以我认为您现在没有对此进行成像，这看起来像是一个错误。
I am using python 3.3, pandas 0.14 and numpy 1.8.1
我正在使用 python 3.3、pandas 0.14 和 numpy 1.8.1
To get around this do this:
要解决这个问题，请执行以下操作：
df = pd.read_csv('MQM Q.csv', usecols=[0,1], parse_dates=True, dayfirst=True, index_col=0)
This will set your index to the Date-Time column which will correctly convert to a datetimeindex.
这会将您的索引设置为日期时间列，该列将正确转换为日期时间索引。
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
回答by Andy Hayden
Your code should read (no need from StringIO on the filename!):
你的代码应该是这样的（不需要从文件名上的 StringIO ！）：
import pandas as pd
Q = pd.read_csv("/cygdrive/c/temp/MQM Q.csv"), header=0, usecols=["Date-Time", "Value"], parse_dates=True, dayfirst=True, index_col=0)
Otherwise/currently pandas is trying to read the string (of the path) in as a DataFrame:
否则/当前熊猫正在尝试将字符串（路径的）作为数据帧读取：
In [11]: pd.read_csv(StringIO("""/cygdrive/c/temp/MQM Q.csv"""))
Out[11]:
Empty DataFrame
Columns: [/cygdrive/c/temp/MQM Q.csv]
Index: []
which obviously isn't what you want (hence you see the Value is not a column exception).
这显然不是您想要的（因此您会看到 Value 不是列异常）。
回答by Hai Vu
The following works for me (I have the CSV file in the same directory as the script, but that should not matter). I am running the following script on my Mac, not Cygwin, but it should work the same way:
以下对我有用（我的 CSV 文件与脚本位于同一目录中，但这应该无关紧要）。我在我的 Mac 上运行以下脚本，而不是 Cygwin，但它应该以相同的方式工作：
import pandas as pd
Q = pd.read_csv("MQM Q.csv",
header=0,
parse_dates=True,
dayfirst=True,
index_col=0,
usecols=["Date-Time", "Value"])
print Q
Discussion
讨论
- StringIO will not work, unless you create a new StringIO object with the contents of the file, not the name of the file.
- I don't have any problem with the "Date-Time" column. In fact, there is not error running the previous code at all.
- StringIO 将不起作用，除非您使用文件的内容而不是文件的名称创建一个新的 StringIO 对象。
- 我对“日期时间”列没有任何问题。事实上，运行之前的代码根本没有错误。
