Question

我正在使用Python 3.3.1。我创建了一个名为download_file()的函数，它下载文件并将其保存到磁盘。

#!/usr/bin/python3
# -*- coding: utf8 -*-

import datetime
import os
import urllib.error
import urllib.request


def download_file(*urls, download_location=os.getcwd(), debugging=False):
    """Downloads the files provided as multiple url arguments.

    Provide the url for files to be downloaded as strings. Separate the
    files to be downloaded by a comma.

    The function would download the files and save it in the folder
    provided as keyword-argument for download_location. If
    download_location is not provided, then the file would be saved in
    the current working directory. Folder for download_location would be
    created if it doesn't already exist. Do not worry about trailing
    slash at the end for download_location. The code would take carry of
    it for you.

    If the download encounters an error it would alert about it and
    provide the information about the Error Code and Error Reason (if
    received from the server).

    Normal Usage:
    >>> download_file('http://localhost/index.html',
                      'http://localhost/info.php')
    >>> download_file('http://localhost/index.html',
                      'http://localhost/info.php',
                      download_location='/home/aditya/Download/test')
    >>> download_file('http://localhost/index.html',
                      'http://localhost/info.php',
                      download_location='/home/aditya/Download/test/')

    In Debug Mode, files are not downloaded, neither there is any
    attempt to establish the connection with the server. It just prints
    out the filename and its url that would have been attempted to be
    downloaded in Normal Mode.

    By Default, Debug Mode is inactive. In order to activate it, we
    need to supply a keyword-argument as 'debugging=True', like:
    >>> download_file('http://localhost/index.html',
                      'http://localhost/info.php',
                      debugging=True)
    >>> download_file('http://localhost/index.html',
                      'http://localhost/info.php',
                      download_location='/home/aditya/Download/test',
                      debugging=True)

    """
    # Append a trailing slash at the end of download_location if not
    # already present
    if download_location[-1] != '/':
        download_location = download_location + '/'

    # Create the folder for download_location if not already present
    os.makedirs(download_location, exist_ok=True)

    # Other variables
    time_format = '%Y-%b-%d %H:%M:%S'   # '2000-Jan-01 22:10:00'

    # "Request Headers" information for the file to be downloaded
    accept = 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8'
    accept_encoding = 'gzip, deflate'
    accept_language = 'en-US,en;q=0.5'
    connection = 'keep-alive'
    user_agent = 'Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:20.0) \
                  Gecko/20100101 Firefox/20.0'
    headers = {'Accept': accept,
               'Accept-Encoding': accept_encoding,
               'Accept-Language': accept_language,
               'Connection': connection,
               'User-Agent': user_agent,
               }

    # Loop through all the files to be downloaded
    for url in urls:
        filename = os.path.basename(url)
        if not debugging:
            try:
                request_sent = urllib.request.Request(url, None, headers)
                response_received = urllib.request.urlopen(request_sent)
            except urllib.error.URLError as error_encountered:
                print(datetime.datetime.now().strftime(time_format),
                      ':', filename, '- The file could not be downloaded.')
                if hasattr(error_encountered, 'code'):
                    print(' ' * 22, 'Error Code -', error_encountered.code)
                if hasattr(error_encountered, 'reason'):
                    print(' ' * 22, 'Reason -', error_encountered.reason)
            else:
                read_response = response_received.read()
                output_file = download_location + filename
                with open(output_file, 'wb') as downloaded_file:
                    downloaded_file.write(read_response)
                print(datetime.datetime.now().strftime(time_format),
                      ':', filename, '- Downloaded successfully.')
        else:
            print(datetime.datetime.now().strftime(time_format),
                  ': Debugging :', filename, 'would be downloaded from :\n',
                  ' ' * 21, url)

此功能适用于下载PDF，图像和其他格式，但它会给文本文档（如html文件）带来麻烦。我怀疑问题必须在最后用这一行做点什么：

with open(output_file, 'wb') as downloaded_file:

所以，我也试过在wt模式下打开它。还尝试过仅使用w模式。但这并没有解决问题。

另一个问题可能是编码所以我还将第二行包含在：

# -*- coding: utf8 -*-

但这仍然无效。可能是什么问题，如何使它适用于文本和二进制文件？

不起作用的示例：

>>>download_file("http://docs.python.org/3/tutorial/index.html")

当我在Gedit中打开它时，它显示为：

in gedit

同样在Firefox中打开时：

in firefox

Answer 1

您下载的文件已使用gzip编码发送 - 您可以看到，如果zcat index.html，则下载的文件会正确显示。在您的代码中，您可能希望添加以下内容：

if response_received.headers.get('Content-Encoding') == 'gzip':
    read_response = zlib.decompress(read_response, 16 + zlib.MAX_WBITS)

编辑：

好吧，我不能说为什么它适用于Windows（不幸的是我没有Windows框来测试它），但是如果你发布了响应的转储（即将响应对象转换为字符串））这可能会提供一些见解。据推测，服务器选择不使用gzip编码发送，但鉴于此代码对标题非常明确，我不确定会有什么不同。

值得一提的是，您的标头明确指定允许使用gzip和deflate（请参阅accept_encoding）。如果删除该标题，则无需担心在任何情况下解压缩响应。

为什么下载文本文件无法正常工作？

1 个答案: