urllib2 POST进度监控

Question

我正在通过POST将带有urllib2的相当大的文件上传到服务器端脚本.我想显示一个显示当前上传进度的进度指示器.是否有urllib2提供的钩子或回调,允许我监控上传进度？我知道您可以通过连续调用连接的read()方法进行下载,但是我没有看到write()方法,只是向请求添加数据.

Answer 1

这是可能的,但你需要做一些事情:

• 将urllib2子系统伪造成将文件句柄传递给httplib,方法是附加一个返回正确大小的__len__属性len(data),用于填充Content-Length标头.
• 覆盖read()文件句柄上的方法:作为httplib read()调用,将调用您的回调,让您计算百分比并更新进度条.

这可以适用于任何类似文件的对象,但我已经打包file以显示它如何与从磁盘流传输的非常大的文件一起工作:

import os, urllib2
from cStringIO import StringIO

class Progress(object):
    def __init__(self):
        self._seen = 0.0

    def update(self, total, size, name):
        self._seen += size
        pct = (self._seen / total) * 100.0
        print '%s progress: %.2f' % (name, pct)

class file_with_callback(file):
    def __init__(self, path, mode, callback, *args):
        file.__init__(self, path, mode)
        self.seek(0, os.SEEK_END)
        self._total = self.tell()
        self.seek(0)
        self._callback = callback
        self._args = args

    def __len__(self):
        return self._total

    def read(self, size):
        data = file.read(self, size)
        self._callback(self._total, len(data), *self._args)
        return data

path = 'large_file.txt'
progress = Progress()
stream = file_with_callback(path, 'rb', progress.update, path)
req = urllib2.Request(url, stream)
res = urllib2.urlopen(req)

输出:

large_file.txt progress: 0.68
large_file.txt progress: 1.36
large_file.txt progress: 2.04
large_file.txt progress: 2.72
large_file.txt progress: 3.40
...
large_file.txt progress: 99.20
large_file.txt progress: 99.87
large_file.txt progress: 100.00