如何读取文件的前N行? [英] How to read first N lines of a file?

问题描述

我们有一个很大的原始数据文件，我们希望将其裁剪为指定的大小.我在.net c#方面经验丰富，但是想在python中做到这一点，以简化事情，并且没有兴趣.

We have a large raw data file that we would like to trim to a specified size. I am experienced in .net c#, however would like to do this in python to simplify things and out of interest.

我该如何在python中获取文本文件的前N行?使用的操作系统会对实施产生影响吗?

How would I go about getting the first N lines of a text file in python? Will the OS being used have any effect on the implementation?

推荐答案

Python 2:

with open("datafile") as myfile:
    head = [next(myfile) for x in xrange(N)]
print head

Python 3:

with open("datafile") as myfile:
    head = [next(myfile) for x in range(N)]
print(head)

这是另一种方式( Python 2和3 ):

from itertools import islice

with open("datafile") as myfile:
    head = list(islice(myfile, N))
print(head)

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