Python urllib2 cookies将打印，但不会打印'；救不了

我可以遍历HTTPS响应的cookies，但无法将它们保存到磁盘。为什么不呢

cookies = cookielib.LWPCookieJar('mycookies.txt')

passman = urllib2.HTTPPasswordMgrWithDefaultRealm()
passman.add_password(None, url, user, password)

handlers = [
    HTTPNtlmAuthHandler.HTTPNtlmAuthHandler(passman),
    urllib2.HTTPHandler(),
    urllib2.HTTPSHandler(),
    urllib2.HTTPCookieProcessor(cookies)
    ]

headers = {
    /* headers go here */
    }

# create and install the opener
opener = urllib2.build_opener(*handlers)

def fetch(uri):
    req = urllib2.Request(uri, headers)
    return opener.open(uri)

def dump():
    for cookie in cookies:
        print cookie.name, cookie.value


# retrieve the result
resp = fetch(url)
dump()
cookies.save()

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当我运行代码时，响应中的cookies会被打印到控制台，但是当我打开

mycokies.txt

文件时，我看到的只是

#LWP-cookies-2.0

找到了答案。最后一行需要如下所示：

cookies = cookielib.LWPCookieJar('myaxis.cookies')