上周发了篇《两条与密码验证相关的正则表达式问题》。今天看了些python的正则表达式，心血来潮，想看看这几种正则哪种效率较高。代码、运行结果见下。这是为什么呢？

#!/usr/bin/python
import re
import time
import fpformat
Regex1 = re.compile("^(?=[0-9a-zA-Z@%&]*\d)(?=[0-9a-zA-Z@%&]*[a-zA-Z])(?=[0-9a-zA-Z@%&]*[@%&])[0-9a-zA-Z@%&]{8,}$", re.MULTILINE)
Regex2 = re.compile("^(?=.*\d)(?=.*[a-zA-Z])(?=.*[@%&])[0-9a-zA-Z@%&]{8,}$", re.MULTILINE)
Regex3 = re.compile("^(?![0-9a-z]{8,16}$|[@%&]{8,16}$)[a-z0-9@%&]{8,16}$", re.IGNORECASE |re.MULTILINE) 
 
 
 
TimesToDo = 1250;
TestString = ""
for i in range(800):
    TestString += "aba134babdedfg@&%\n"
 
StartTime = time.time()
for i in range(TimesToDo):
   Regex1.search(TestString)
Seconds = time.time() - StartTime
print "R1 takes " + fpformat.fix(Seconds,3) + " seconds"
 
StartTime = time.time()
for i in range(TimesToDo):
   Regex2.search(TestString)
Seconds = time.time() - StartTime
print "R2 takes " + fpformat.fix(Seconds,3) + " seconds"
 
StartTime = time.time()
for i in range(TimesToDo):
   Regex3.search(TestString)
Seconds = time.time() - StartTime
print "R3 takes " + fpformat.fix(Seconds,3) + " seconds"

运行结果：
我爱正则表达式|效率问题