搜索文件的最后X行的最有效方法？

Question

我有一个文件，但我不知道它会有多大（可能会很大，但是大小会相差很大）。我想搜索最后10行左右，以查看它们是否与字符串匹配。我需要尽快高效地执行此操作，并且想知道是否还有什么比以下更好的：

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

Answer 1

# 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