python3提取指定字段

def txt_wrap_by(start_str, end, html):
    #提取俩个字符间的东西
    start = html.find(start_str)
    if start >= 0:
        start += len(start_str)
        end = html.find(end, start)
        if end >= 0:
            return html[start:end].strip()
def txt_wrap_by2(start_str,end_str,html):
    #通过切片提取指定字符
    start=html.find(start_str)
    end = html.find((end_str),len(end_str)+start)
    return html[start:end]
#     start = s.find('image_url')  
# end = s.find('>', len('image_url')+start)
# s[start:end]
 
 
if __name__=="__main__":
    filename="C:/Users/Desktop/info.2018" 
    f1 = open(filename,encoding='utf-8')
    newDate=''
    while True:
        line=f1.readline()
        if (not line):
            break
        newDate+=txt_wrap_by2("<title:",">",line)
        print(newDate)