python gbk中国語文字の取得

# -*- coding: gbk -*-

def getGBK(s):    
    i = 0
    first = (int('81',16),int('FE',16))
    second1 = (int('40',16),int('7E',16))
    second2= (int('80',16),int('FE',16))    
    buf = []
    while True:
        ch1 = ord(s[i])        
        if ch1 >= first[0] and ch1 <= first[1]:            
            i = i + 1
            if i >= len(s):
                break
            ch2 = ord(s[i])
            if (ch2 >= second1[0] and ch2 <= second1[1]) or \
               (ch2 >= second2[0] and ch2 <= second2[1]):
                buf.append(chr(ch1))
                buf.append(chr(ch2))
                i = i + 1
        else:
            i = i + 1
        if i >= len(s):
            break
    print ''.join(buf)
    
                
            
getGBK('     ')
getGBK('@    %$%')
getGBK('@ abc  %$%')    

実行結果
C:\>test.py私は誰ですか私は誰ですか私は誰ですか