如何实现一个pythonic等效的tail -F？ [英] How to implement a pythonic equivalent of tail -F?

问题描述

在shell中我可能会说：

  tail -f$ file| grep$ string|同时读命中;做
 #stuff 
 done 
  

解决方案

嗯，最简单的方法是不断从文件中读取，检查新功能并测试命中。

  import time 
 
 def watch（fn，words）：
 fp = open（fn，'r'）
 while True：
 new = fp.readline（）
＃一旦所有的行被读取，这只是返回''
＃，直到文件更改，并出现一个新行
 
如果新：
为单词中的单词：
如果在新的单词：
 yield（word，new）
 else：
 time.sleep（0.5）
 
 fn ='test.py'
 word = ['word'] 
 for hit_word，hit_sentence in watch（fn，words）：
 print找到％r in行：％r％（hit_word，hit_sentence）
  

如果您知道您的数据将以线条出现，此解决方案可以使用 readline 。

如果数据是某种流，则需要一个缓冲区，大于最大的字为，并填写它。它的方式有点复杂...

What is the pythonic way of watching the tail end of a growing file for the occurrence of certain keywords?

In shell I might say:

tail -f "$file" | grep "$string" | while read hit; do
    #stuff
done

解决方案

Well, the simplest way would be to constantly read from the file, check what's new and test for hits.

import time

def watch(fn, words):
    fp = open(fn, 'r')
    while True:
        new = fp.readline()
        # Once all lines are read this just returns ''
        # until the file changes and a new line appears

        if new:
            for word in words:
                if word in new:
                    yield (word, new)
        else:
            time.sleep(0.5)

fn = 'test.py'
words = ['word']
for hit_word, hit_sentence in watch(fn, words):
    print "Found %r in line: %r" % (hit_word, hit_sentence)

This solution with readline works if you know your data will appear in lines.

If the data is some sort of stream you need a buffer, larger than the largest word you're looking for, and fill it first. It gets a bit more complicated that way...

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