Python-挑战级别 3

问题是:一封小信，两边各围着三名大个子保镖。 我写了这段代码并得到了答案。我认为这是正确的，但它不起作用。有谁能够帮助我？我的回答:KWGtIDC

import urllib, sys, string 
from string import maketrans 
 
bbb = 0 
 
f = urllib.urlopen("http://www.pythonchallenge.com/pc/def/equality.html") 
while 1: 
    buf = f.read(200000) 
    if not len(buf): 
        break 
    for x in range(len(buf)): 
        if buf[x] in string.ascii_lowercase: 
           if buf[x+1] in string.ascii_uppercase: 
               if buf[x-1] in string.ascii_uppercase: 
                   if buf[x+2] in string.ascii_uppercase: 
                       if buf[x-2] in string.ascii_uppercase: 
                           if buf[x+3] in string.ascii_uppercase: 
                               if buf[x-3] in string.ascii_uppercase: 
                                   if buf[x+4] in string.ascii_lowercase: 
                                       if buf[x-4] in string.ascii_lowercase: 
                                           bbb = x 
    sys.stdout.write(buf) 
    print(buf[bbb-3:bbb+4])