Most efficient way to search the last X lines of a file?

Question

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" 

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