使用urllib3进行多部分表单编码和发布

Question

我正在尝试将csv文件上载到this site。然而，我遇到了一些问题，我认为它源于不正确的mimetype（可能）。

我正试图通过urllib2手动发布文件，因此我的代码如下所示：

import urllib
import urllib2
import mimetools, mimetypes
import os, stat
from cStringIO import StringIO

#============================
# Note: I found this recipe online. I can't remember where exactly though.. 
#=============================

class Callable:
    def __init__(self, anycallable):
        self.__call__ = anycallable

# Controls how sequences are uncoded. If true, elements may be given multiple values by
#  assigning a sequence.
doseq = 1

class MultipartPostHandler(urllib2.BaseHandler):
    handler_order = urllib2.HTTPHandler.handler_order - 10 # needs to run first

    def http_request(self, request):
        data = request.get_data()
        if data is not None and type(data) != str:
            v_files = []
            v_vars = []
            try:
                 for(key, value) in data.items():
                     if type(value) == file:
                         v_files.append((key, value))
                     else:
                         v_vars.append((key, value))
            except TypeError:
                systype, value, traceback = sys.exc_info()
                raise TypeError, "not a valid non-string sequence or mapping object", traceback

            if len(v_files) == 0:
                data = urllib.urlencode(v_vars, doseq)
            else:
                boundary, data = self.multipart_encode(v_vars, v_files)

                contenttype = 'multipart/form-data; boundary=%s' % boundary
                if(request.has_header('Content-Type')
                   and request.get_header('Content-Type').find('multipart/form-data') != 0):
                    print "Replacing %s with %s" % (request.get_header('content-type'), 'multipart/form-data')
                request.add_unredirected_header('Content-Type', contenttype)

            request.add_data(data)

        return request

    def multipart_encode(vars, files, boundary = None, buf = None):
        if boundary is None:
            boundary = mimetools.choose_boundary()
        if buf is None:
            buf = StringIO()
        for(key, value) in vars:
            buf.write('--%s\r\n' % boundary)
            buf.write('Content-Disposition: form-data; name="%s"' % key)
            buf.write('\r\n\r\n' + value + '\r\n')
        for(key, fd) in files:
            file_size = os.fstat(fd.fileno())[stat.ST_SIZE]
            filename = fd.name.split('/')[-1]
            contenttype = mimetypes.guess_type(filename)[0] or 'application/octet-stream'
            buf.write('--%s\r\n' % boundary)
            buf.write('Content-Disposition: form-data; name="%s"; filename="%s"\r\n' % (key, filename))
            buf.write('Content-Type: %s\r\n' % contenttype)
            # buffer += 'Content-Length: %s\r\n' % file_size
            fd.seek(0)
            buf.write('\r\n' + fd.read() + '\r\n')
        buf.write('--' + boundary + '--\r\n\r\n')
        buf = buf.getvalue()
        return boundary, buf
    multipart_encode = Callable(multipart_encode)

    https_request = http_request

    import cookielib
    cookies = cookielib.CookieJar()
    opener = urllib2.build_opener(urllib2.HTTPCookieProcessor(cookies),
            MultipartPostHandler)

    opener.addheaders = [(
            'User-agent', 
            'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.6) Gecko/20070725 Firefox/2.0.0.6'
        )]


    params = {"FILENAME" : open("weather_scrape.csv", 'rb'),
            'CGIREF' : '/calludt.cgi/DDFILE1',
            'USE':'MODEL',
            'MODEL':'CM',
            'CROP':'APPLES',
            'METHOD': 'SS',
            'UNITS' : 'E',
            'LOWTHRESHOLD': '50',
            'UPTHRESHOLD': '88',
            'CUTOFF':'H',
            'COUNTY':'AL',
            'ACTIVE':'Y',
            'FROMMONTH':'3',
            'FROMDAY':'15',
            'FROMYEAR': '2013',
            'THRUMONTH':'5',
            'THRUDAY':'13',
            'THRUYEAR':'2013',
            'DATASOURCE' : 'FILE'
            }

    response = opener.open("http://www.ipm.ucdavis.edu/WEATHER/textupload.cgi", params)

现在，当我发布这篇文章时，一切似乎都很好，直到我单击第一个POST返回的后续网页上的submit按钮。然后我会收到以下错误消息：

ERROR (bad data) in file 'weather.csv' at line 135.

Data record = [--192.168.117.2.1.4404.1368589639.796.1--]

Too few values found. Check delimiter specification.

现在，在调查我在浏览器中执行操作时发出的post请求时，我注意到content-type非常具体，即：

------WebKitFormBoundaryfBp6Jfhv7LlPZLKd
Content-Disposition: form-data; name="FILENAME"; filename="weather.csv"
Content-Type: application/vnd.ms-excel

我不完全确定是内容类型导致了错误，但是。。这是我目前正在排除的（因为我不知道到底出了什么问题。）我看不到任何可以通过urllib2设置内容类型的方法，所以在一些搜索之后，我偶然发现了urllib3.

Urllib3具有内置文件发布功能，但我不完全确定如何使用它。

Filepost

urllib3.filepost.encode_multipart_formdata(fields, boundary=None)
Encode a dictionary of fields using the multipart/form-data MIME format.

Parameters: 
fields –
Dictionary of fields or list of (key, value) or (key, value, MIME type) field tuples. The key is treated as the field name, and the value as the body of the form-data bytes. If the value is a tuple of two elements, then the first element is treated as the filename of the form-data section and a suitable MIME type is guessed based on the filename. If the value is a tuple of three elements, then the third element is treated as an explicit MIME type of the form-data section.
Field names and filenames must be unicode.
boundary – If not specified, then a random boundary will be generated using mimetools.choose_boundary().
urllib3.filepost.iter_fields(fields)
Iterate over fields.

Supports list of (k, v) tuples and dicts.

使用这个库，我尝试将这些值编码为doc中的decribes，但是我得到了一些错误。

我最初只是想测试一下，作为一个dict。

params = {"FILENAME" : open("weather.csv", 'rb'),
            'CGIREF' : '/calludt.cgi/DDFILE1',
            'USE':'MODEL',
            'MODEL':'CM',
            'CROP':'APPLES',
            'METHOD': 'SS',
            'UNITS' : 'E',
            'LOWTHRESHOLD': '50',
            'UPTHRESHOLD': '88',
            'CUTOFF':'H',
            'COUNTY':'AL',
            'ACTIVE':'Y',
            'FROMMONTH':'3',
            'FROMDAY':'15',
            'FROMYEAR': '2013',
            'THRUMONTH':'5',
            'THRUDAY':'13',
            'THRUYEAR':'2013',
            'DATASOURCE' : 'FILE'
            }

    values = urllib3.filepost.encode_multipart_formdata(params)

但是，这会导致以下错误：

    values = urllib3.filepost.encode_multipart_formdata(params)
  File "c:\python27\lib\site-packages\urllib3-dev-py2.7.egg\urllib3\filepost.py", line 90, in encode_multipart_formdata
    body.write(data)
TypeError: 'file' does not have the buffer interface

不确定是什么原因导致的，我尝试传入一个元组列表（key、value、mimetype），但这也会引发一个错误：

params = [
        ("FILENAME" , open("weather_scrape.csv"), 'application/vnd.ms-excel'),
        ('CGIREF' , '/calludt.cgi/DDFILE1'),
        ('USE','MODEL'),
        ('MODEL','CM'),
        ('CROP','APPLES'),
        ('METHOD', 'SS'),
        ('UNITS' , 'E'),
        ('LOWTHRESHOLD', '50'),
        ('UPTHRESHOLD', '88'),
        ('CUTOFF','H'),
        ('COUNTY','AL'),
        ('ACTIVE','Y'),
        ('FROMMONTH','3'),
        ('FROMDAY','15'),
        ('FROMYEAR', '2013'),
        ('THRUMONTH','5'),
        ('THRUDAY','13'),
        ('THRUYEAR','2013'),
        ('DATASOURCE' , 'FILE)')
        ]

    values = urllib3.filepost.encode_multipart_formdata(params)



>>ValueError: too many values to unpack