help me!!!!!!!!!!!!!!!!

line =urllib.urlopen(url)               
line=line.read()
line=line.replace("\n","").replace("\r","").replace(" <br> ","")
Memo=Get_Table1(line,r""" <span class=\"f14 lh150\"> (.*?) </span> """)#公司名称
上页那段代码执行的时候老是报这个错,很没有规律,特向各位高手求救
'NoneType' object has no attribute 'read'