我正在从一个文件夹导入csv文件，每个文件每10个复制一行。第一行和两列（日期时间，值）有标头，以逗号分隔。当我为单个文件运行代码时，它可以按预期工作：
frequency=pd.read_csv("DK_Frequency/2019-04-11.csv")
li = []
li.append(frequency.iloc[::10])
li
Time Value
0 2019-04-11 00:00:00.000 50.022
10 2019-04-11 00:00:01.000 50.023
20 2019-04-11 00:00:02.000 50.021
30 2019-04-11 00:00:03.000 50.022
40 2019-04-11 00:00:04.000 50.022
50 2019-04-11 00:00:05.000 50.023
60 2019-04-11 00:00:06.000 50.021
70 2019-04-11 00:00:07.000 50.023
当我使用以下方法进入文件夹时：
all_files = glob.glob("DK_Frequency/*.csv")
li = []
for i in range(len(all_files):
frequency= pd.read_csv(all_files[i])
li.append(frequency.iloc[::10])
甚至：
all_files = glob.glob("DK_Frequency/*.csv")
li = []
for file in all_files :
frequency= pd.read_csv(file)
li.append(frequency.iloc[::10])
我收到错误：
Traceback (most recent call last):
File "<stdin>", line 2, in <module>
File "/usr/local/lib/python2.7/dist-packages/pandas/io/parsers.py", line 646, in parser_f
return _read(filepath_or_buffer, kwds)
File "/usr/local/lib/python2.7/dist-packages/pandas/io/parsers.py", line 389, in _read
parser = TextFileReader(filepath_or_buffer, **kwds)
File "/usr/local/lib/python2.7/dist-packages/pandas/io/parsers.py", line 730, in __init__
self._make_engine(self.engine)
File "/usr/local/lib/python2.7/dist-packages/pandas/io/parsers.py", line 923, in _make_engine
self._engine = CParserWrapper(self.f, **self.options)
File "/usr/local/lib/python2.7/dist-packages/pandas/io/parsers.py", line 1390, in __init__
self._reader = _parser.TextReader(src, **kwds)
File "pandas/parser.pyx", line 538, in pandas.parser.TextReader.__cinit__ (pandas/parser.c:5902)
pandas.io.common.EmptyDataError: No columns to parse from file
关于如何解决此问题的任何想法？