Python:命中字符串时从文本文件中打印下x条线 [英] Python: Print next x lines from text file when hitting string

问题描述

情况如下:

我有一个.txt文件，其结果是多个nslookups.

I have a .txt file with results of several nslookups.

我想循环tru文件，并在每次命中字符串非权威性答案:"时，脚本必须从该位置 打印以下8行.如果可以，我应该在屏幕上获得所有积极的结果:).

I want to loop tru the file and everytime it hits the string "Non-authoritative answer:" the scripts has to print the following 8 lines from that position. If it works I shoud get all the positive results in my screen :).

首先，我有以下代码:

#!/bin/usr/python

file = open('/tmp/results_nslookup.txt', 'r')
f = file.readlines()

for positives in f:
        if 'Authoritative answers can be found from:' in positives:
                print positives
file.close()

但是，只有打印出来的权威性答案可以从:"中找到，即出现在.txt中的时间.

But that only printed "Authoritative answers can be found from:" the times it was in the .txt.

我现在拥有的代码:

#!/bin/usr/python

file = open('/tmp/results_nslookup.txt', 'r')
lines = file.readlines()

i = lines.index('Non-authoritative answer:\n')

for line in lines[i-0:i+9]:
        print line,

file.close()

但是，当我运行它时，它会很好地将第一个结果打印到我的屏幕上，但不会打印其他正向结果.

But when I run it, it prints the first result nicely to my screen but does not print the other positve results.

p.s.我知道socket.gethostbyname("foobar.baz")，但首先我想解决这个基本问题.

p.s. I am aware of socket.gethostbyname("foobar.baz") but first I want to solve this basic problem.

提前谢谢！

推荐答案

您可以将该文件用作迭代器，然后在每次找到句子时打印接下来的8行:

You can use the file as an iterator, then print the next 8 lines every time you find your sentence:

with open('/tmp/results_nslookup.txt', 'r') as f:
    for line in f:
        if line == 'Non-authoritative answer:\n':
            for i in range(8):
                print(next(lines).strip())

每次您都在屏幕上使用 next()函数文件对象(或在for循环中循环)，它将返回该文件的下一行，直到您读取了最后一行.

Each time you use the next() function on the file object (or loop over it in a for loop), it'll return the next line in that file, until you've read the last line.

实际上，我会使用itertools.islice:

from itertools import islice

with open('/tmp/results_nslookup.txt', 'r') as f:
    for line in f:
        if line == 'Non-authoritative answer:\n':
            print(''.join(islice(f, 8)))

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