python - 在 python 中使用 mechanize 似乎不适用于 POST 请求。（400 错误）

Question

我正在用 Python 编写一个 IRC 机器人，以便我和我的朋友从 Steam 市场购买物品。它主要是为了好玩和提高我的编程技能。我已经能够获得一件商品的最低价格，但我在发布购买请求时遇到了问题。我发出了会话 id 和 steamLogin cookie，url 可以是http://steamcommunity.com/market/listings/730/Winter%20Offensive%20Weapon%20Case. 这是蒸汽部分的代码：

import mechanize, re, datetime, urllib
from cookielib import Cookie
from cookielib import LWPCookieJar

url = 'http://steamcommunity.com/market/listings/730/blahblah'
sessionid = ''
steamLogin = ''
maximum = int(raw_input('How much are you willing to pay? '))

def makeCookie(name, value):
    return Cookie(
        version=0, 
        name=name, 
        value=value,
        port=None, 
        port_specified=False,
        domain="steamcommunity.com", 
        domain_specified=True, 
        domain_initial_dot=False,
        path="/", 
        path_specified=True,
        secure=False,
        expires=None,
        discard=False,
        comment=None,
        comment_url=None,
        rest=None
    )

br = mechanize.Browser()

cj = LWPCookieJar()
br.set_cookiejar(cj)
cj.set_cookie(makeCookie('sessionid', sessionid))
cj.set_cookie(makeCookie('steamLogin', steamLogin))
br.addheaders = [('User-agent', 'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.7) Gecko/20100713 Firefox/3.6.7')]

id = ''
response = br.open(url)
elements = response.read().splitlines()
line = (elements[elements.index('\tvar g_rgCurrency = [];') + 1])[23:]
match = re.search(r'("listingid":")(\d+)(.+?)(converted_price":)(\d+)(,"converted_fee":)(\d+)', line)
if not match: continue
if match.group(2) == id: continue
id = match.group(2)
subtotal = int(match.group(5))
fee = int(match.group(7))
total = subtotal + fee
print "Total at", str(datetime.datetime.now()) + ' for listing id (' + id + '):', '${:,.2f}'.format(float(total)/100)
if total <= maximum:
    data = urllib.urlencode({'sessionid': sessionid,
    'currency': '1',
    'subtotal': subtotal,
    'fee': fee,
    'total': total})
    print data
    try:
        post = br.open('https://steamcommunity.com/market/buylisting/' + id, data)
    except Exception as e:
        print e