python-亚马逊接口签名问题 急！！！

访问亚马逊的接口在签名这里一直提示他们计算的签名于我计算的不符，但是我不知道我操作在哪里出现了问题

以下是签名规则

官方文档

我的代码

import requests
import datetime
import hashlib
def urlEncode(url):
    url.replace("+","%20")
    url.replace("*","%2A")
    url.replace(":","%3A")
    return url
secretKey = "";
serviceUrl = "https://mws.amazonservices.com/";
data = {
    'AWSAccessKeyId':'',
    'Action':'GetReportCount',
    'MWSAuthToken':'',
    'SellerId':'',
    'SignatureMethod':'HmacSHA256',
    'SignatureVersion':'2',
    'Timestamp':datetime.datetime.utcnow().isoformat(),
    'Version':'2009-01-01',
}
a = "&".join(["{0}={1}".format(k, data[k]) for k in sorted(data)])
a = urlEncode(a)
key = "POST\n"+"mws.amazonservices.com\n"+"/\n"+a
sha256 = hashlib.sha256("t+qpwMTc9sZfW2unRXkhDdVlFoL7pUxKZSs4cXSH".encode("utf-8"))
sha256.update(key.encode("utf-8"))
key = sha256.hexdigest()
import base64
k = str(base64.b64encode(key.encode("utf-8")),"utf-8")
data = {
    'AWSAccessKeyId':'',
    'Action':'GetReportCount',
    'MWSAuthToken':'',
    'SellerId':'',
    "Signature":k,
    'SignatureMethod':'HmacSHA256',
    'SignatureVersion':'2',
    'Timestamp':datetime.datetime.utcnow().isoformat(),
    'Version':'2009-01-01',
}
response = requests.post(serviceUrl,data =data )

加密地方有问题，注意要求的加密方式

签名有问题了，看一下签名的规则