urllib2 POST进度监控 [英] urllib2 POST progress monitoring

问题描述

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？我知道你可以通过连续调用连接的read（）方法来下载，但我没有看到write（）方法，你只需要向请求中添加数据。

I'm uploading a fairly large file with urllib2 to a server-side script via POST. I want to display a progress indicator that shows the current upload progress. Is there a hook or a callback provided by urllib2 that allows me to monitor upload progress? I know that you can do it with download using successive calls to the connection's read() method, but I don't see a write() method, you just add data to the request.

推荐答案

这是可能的，但你需要做一些事情：

It is possible but you need to do a few things:

• 假urllib2子系统通过附加 __ len __ 属性将文件句柄传递给httplib，这使得 len（data）返回正确的大小，用于填充Content-Length标头。


• 覆盖文件句柄上的 read（）方法：as httplib调用 read（）将调用您的回调，让您计算百分比并更新进度条。

• Fake out the urllib2 subsystem into passing a file handle down to httplib by attaching a __len__ attribute which makes len(data) return the correct size, used to populate the Content-Length header.
• Override the read() method on your file handle: as httplib calls read() your callback will be invoked, letting you calculate the percentage and update your progress bar.

这可以用于任何类似文件的对象，但是我已经包装了文件来展示如何使用从磁盘流式传输的非常大的文件：

This could work with any file-like object, but I've wrapped file to show how it could work with a really large file streamed from disk:

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

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