引用codecs模組，來判斷前三個位元組是否為BOM_UTF8。如果是，則剔除\xef\xbb\xbf位元組

import codecs
def download_ipurl(self,destpath):
    try:
        f = open(destpath,'r')
        iter_f = iter(f)
        lines = 0
        for ipurl in iter_f:
            lines = lines + 1
            if ipurl[0:3] == codecs.BOM_UTF8:    
                self.newipurls.add((ipurl.rstrip('\r\n')).lstrip('\xef\xbb\xbf'))
        #print self.newipurls
        #log記錄讀取了多少行IP url
        #print lines
    finally:
        if f:
            f.close()