我需要用python讀取一個.dat文件，它總共有12列，數百萬行。我需要把第2、3和4欄和第1欄分開計算。所以在加載.dat文件之前，是否需要刪除所有其他不需要的列？如果沒有，如何有選擇地聲明列并要求python進行計算？

.dat文件的一個例子是

data.dat

我對python還不熟悉，所以有點關于打開、閱讀和計算的指導會很感激。

我已經根據您的建議添加了我作為初學者使用的代碼：from sys import argv

import pandas as pd

script, filename = argv

txt = open(filename)

print "Here's your file %r:" % filename

print txt.read()

def your_func(row):

return row['x-momentum'] / row['mass']

columns_to_keep = ['mass', 'x-momentum']

dataframe = pd.read_csv('~/Pictures', delimiter="," , usecols=columns_to_keep)

dataframe['new_column'] = dataframe.apply(your_func, axis=1)

還有我犯的錯誤：Traceback (most recent call last):

File "flash.py", line 18, in

dataframe = pd.read_csv('~/Pictures', delimiter="," , usecols=columns_to_keep)

File "/home/trina/anaconda2/lib/python2.7/site-packages/pandas/io/parsers.py", line 529, in parser_f

return _read(filepath_or_buffer, kwds)

File "/home/trina/anaconda2/lib/python2.7/site-packages/pandas/io/parsers.py", line 295, in _read

parser = TextFileReader(filepath_or_buffer, **kwds)

File "/home/trina/anaconda2/lib/python2.7/site-packages/pandas/io/parsers.py", line 612, in __init__

self._make_engine(self.engine)

File "/home/trina/anaconda2/lib/python2.7/site-packages/pandas/io/parsers.py", line 747, in _make_engine

self._engine = CParserWrapper(self.f, **self.options)

File "/home/trina/anaconda2/lib/python2.7/site-packages/pandas/io/parsers.py", line 1119, in __init__

self._reader = _parser.TextReader(src, **kwds)

File "pandas/parser.pyx", line 518, in pandas.parser.TextReader.__cinit__ (pandas/parser.c:5030)

ValueError: No columns to parse from file

總結

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