请求response.iter_content()得到不完整的文件(1024MB而不是1.5GB)？

您好我一直在使用此代码段从网站下载文件,到目前为止,小于1GB的文件都很好.但我注意到1.5GB的文件不完整

# s is requests session object
r = s.get(fileUrl, headers=headers, stream=True)

start_time = time.time()
with open(local_filename, 'wb') as f:
    count = 1
    block_size = 512
    try:
        total_size = int(r.headers.get('content-length'))
        print 'file total size :',total_size
    except TypeError:
        print 'using dummy length !!!'
        total_size = 10000000

    for chunk in r.iter_content(chunk_size=block_size):

        if chunk:  # filter out keep-alive new chunks

            duration = time.time() - start_time
            progress_size = int(count * block_size)
            if duration == 0:
                duration = 0.1
            speed = int(progress_size / (1024 * duration))
            percent = int(count * block_size * 100 / total_size)
            sys.stdout.write("\r...%d%%, %d MB, %d KB/s, %d seconds passed" %
                            (percent, progress_size / (1024 * 1024), speed, duration))

            f.write(chunk)
            f.flush()
            count += 1

使用最新请求2.2.1 python 2.6.6,centos 6.4文件下载总是停在66.7%1024MB,我缺少什么？输出:

file total size : 1581244542
...67%, 1024 MB, 5687 KB/s, 184 seconds passed

似乎iter_content()返回的生成器认为检索了所有块并且没有错误.顺便说一下,异常部分没有运行,因为服务器确实在响应头中返回了内容长度.