Python海报内容长度错误

Question

我在尝试用poster这个模块发送图片。虽然我按照示例来做，但对我来说并没有成功。

我的代码是：

from poster.encode import multipart_encode
from poster.streaminghttp import register_openers
import urllib, urllib2

def decaptcha(hash):
register_openers()

    params = {
        "file": open("captcha.jpg", "rb"),
        "function" : "picture2",
        "username" : "uname",
        "password" : "pwd",
        "pict_to" : 0,
        "pict_type" : 0
        }


    datagen, headers = multipart_encode(params)

    req = urllib2.Request("http://poster.decaptcher.com/")

    solve = urllib2.urlopen(req, datagen, headers)
    print solve.read()

decaptcha(None)

还有错误信息：

`File "decaptcha.py", line 27, in <module>
    decaptcha(None)
  File "decaptcha.py", line 24, in decaptcha
    solve = urllib2.urlopen(req, datagen, headers)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib2.py", line 126, in urlopen
    return _opener.open(url, data, timeout)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib2.py", line 390, in open
    req = meth(req)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/poster-0.8.1-py2.7.egg/poster/streaminghttp.py", line 154, in http_request
    "No Content-Length specified for iterable body")
ValueError: No Content-Length specified for iterable body`

Answer 1

你应该把数据生成器（datagen）和请求头（headers）传给请求，而不是直接传给urlopen：

req = urllib2.Request("http://poster.decaptcher.com/", datagen, headers)
solve = urllib2.urlopen(req)

Answer 2

(免责声明：我没有使用过poster库。以下建议是我最好的猜测。)

从poster的文档来看，这个方法应该是可行的。

我会尝试以下方法（传递文件的内容，而不是打开文件的迭代器，这样应该能解决可迭代主体的问题）：

params = {
    "file": open("captcha.jpg", "rb").read(),
    "function" : "picture2",
    "username" : "uname",
    "password" : "pwd",
    "pict_to" : 0,
    "pict_type" : 0
    }

建议2：

或者可以试试： from multipart.encode import MultiPartParam

params = [
    MultiPartParam("file", fileobj=open("captcha.jpg", "rb")),
    ("function", picture2"),
    ("username", "uname"),
    ("password", "pwd"),
    ("pict_to", 0),
    ("pict_type", 0),
]

如果这样还是出现同样的错误，可以尝试给MultiPartParam指定filesize参数。