最有效的方法来搜索python中文件的最后一行 [英] Most efficient way to search the last x lines of a file in python

问题描述

我有一个文件，我不知道它会有多大（可能会很大，但是大小会有很大差异）。我想搜索最近的10行，看看它们是否匹配一个字符串。我需要尽可能快速有效地做到这一点，并且想知道是否有更好的东西：

  s =foo
 last_bit = fileObj.readlines（）[ -  10：] 
在last_bit中的行：
如果行== s：
打印FOUND
  

解决方案

 ＃尾
从__future__导入with_statement 
 
 find_str =FIREFOX＃字符串查找
 fname =g：/autoIt/ActiveWin.log_2＃文件检查
 
 with open（fname， r）as f：
 f.seek（0，2）＃Seek @ EOF 
 fsize = f.tell（）＃获取大小
 f.seek（max（fsize-1024 ，0），0）＃设置pos @ last n chars 
 lines = f.readlines（）＃读取结束
 
 lines = lines [-10：]＃获取最后10行
 
＃如果任何行完全是find_str +\\\

打印find_str +\\\
在行
 
＃如果你是为li搜索一个子串
 ne行：
如果find_str在行中：
 print True 
 break 
  

I have a file and I don't know how big it's going to be (it could be quite large, but the size will vary greatly). I want to search the last 10 lines or so to see if any of them match a string. I need to do this as quickly and efficiently as possible and was wondering if there's anything better than:

s = "foo"
last_bit = fileObj.readlines()[-10:]
for line in last_bit:
    if line == s:
        print "FOUND"

解决方案

# Tail
from __future__ import with_statement

find_str = "FIREFOX"                    # String to find
fname = "g:/autoIt/ActiveWin.log_2"     # File to check

with open(fname, "r") as f:
    f.seek (0, 2)           # Seek @ EOF
    fsize = f.tell()        # Get Size
    f.seek (max (fsize-1024, 0), 0) # Set pos @ last n chars
    lines = f.readlines()       # Read to end

lines = lines[-10:]    # Get last 10 lines

# This returns True if any line is exactly find_str + "\n"
print find_str + "\n" in lines

# If you're searching for a substring
for line in lines:
    if find_str in line:
        print True
        break

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