添加了一个方法4，同时发现我的电脑上第三种方法要快一些
D:\home\work\python\files>countLines.py
linecount_1 49238
linecount_2 49238
linecount_3 49238
linecount_4 49238
linecount_1: 0.18
linecount_2: 0.16
linecount_3: 0.09
linecount_4: 0.16

D:\home\work\python\files>countLines.py
linecount_1 379813
linecount_2 379813
linecount_3 379813
linecount_4 379813
linecount_1: 1.61
linecount_2: 1.36
linecount_3: 0.85
linecount_4: 1.33

# -*- coding: utf-8 -*-
import time
def timeo(fun, n=10):
    start = time.clock()
    for i in range(n): fun()
    stend = time.clock()
    thetime = stend-start
    return fun.__name__, thetime                        #返回函数名称，函数运行10次总时间的 元组

import os

fname=”YourFileName” #稍微改了一下，添加了一个文件名变量

def linecount_wc():
    return int(os.popen(‘wc -l nuc’).read().split()[0]) #使用外部系统程序 wc -l

def linecount_1( ):                                      #使用方法1  
    return len(open(fname).readlines())                 

def linecount_2():                                      #使用方法2    
    count = 0
    for line in open(fname).xreadlines(): count += 1
    return count

def linecount_3():                                      #使用方法3   
    count = 0
    thefile = open(fname)
    while 1:
        buffer = thefile.read(65536)
        if not buffer: break
        count += buffer.count(‘\n’)
    return count

def linecount_4():   #添加的方法4
    count=0
    for line in open(fname):
        #if(line!=’\n’): count+=1
        count+=1
    return count

for f in linecount_1, linecount_2, linecount_3,linecount_4:
    print f.__name__, f()

for f in linecount_1, linecount_2, linecount_3,linecount_4:
    print “%s: %.2f”%timeo(f)

转自：【浸在苏打水里的玩偶 】http://hi.baidu.com/javalang/blog/item/b2f398efa62acfeccf1b3eb6.html