python 读取缓存文件夹下的csv 出错了，具体代码如下：

import numpy
from matplotlib.mlab import csv2rec
from pylab import figure, show
import matplotlib.cbook as cbook
from matplotlib.ticker import Formatter

datafile = 'C:\.matplotlib\sample_data\601988.csv'
r = csv2rec(datafile)[-40:]
class MyFormatter(Formatter):
    def __init__(self, dates, fmt='%Y-%m-%d'):
        self.dates = dates
        self.fmt = fmt

    def __call__(self, x, pos=0):
        'Return the label for time x at position pos'
        ind = int(round(x))
        print x
        if ind>=len(self.dates) or ind<0: return ''

        return self.dates[ind].strftime(self.fmt)

formatter = MyFormatter(r.date)
fig = figure()
ax = fig.add_subplot(111)
ax.xaxis.set_major_formatter(formatter)
ax.plot(numpy.arange(len(r)), r.close, 'o-')
fig.autofmt_xdate()
show()

运行出现raceback (most recent call last):
  File "F:\practice-py\cbook2.py", line 8, in <module>
    r = csv2rec(datafile)[-40:]
  File "F:\python\lib\site-packages\matplotlib\mlab.py", line 2140, in csv2rec
    fh = cbook.to_filehandle(fname)
  File "F:\python\lib\site-packages\matplotlib\cbook.py", line 434, in to_filehandle
    fh = file(fname, flag)
IOError: [Errno 2] No such file or directory: 'C:\\.matplotlib\\sample_data.csv'

我的文件是存储在C:\.matplotlib\sample_data下的

用datafile = r'C:\.matplotlib\sample_data\601988.csv'

否则字符串中的\是用来转义的，会导致路径不正确。