[GoogleAppEngine][Python]amazon product advertising apiのBrowseNodeLookupを実装

昨日のエントリーと同じになってしまうが、後で、検索しやすいようにタイトルを変えて書いてみた。

下のコードは、google app engineのpythonを使ってamazon product advertising apiのBrowseNodeLookupをコールする処理です。

#!/usr/bin/env python
#
# Copyright 2007 Google Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

from urlparse import urlparse
import urllib
import datetime
import base64
import hmac
import hashlib

amazon_api_access_key_id = "ここにはaccess_key_id"
amazon_api_secret_access_key = "ここにはsecret_access_key"
amazon_api_associatetag = "ここにはassociatetag"
amazon_api_product_advertising_request_url = "http://webservices.amazon.co.jp/onca/xml"
amazon_api_service = "AWSECommerceService"
amazon_api_browsenodelookup = "BrowseNodeLookup"
amazon_api_browsenode_book = "ここにはbrowse node"

def urlencode_rfc3986(str):
  s = urllib.quote(str)
  s = s.replace("%7E", "~")
  return s

def create_canonical_string(d):
  keys = sorted(d)
  canonical_string = ""
  for k in keys:
      canonical_string = canonical_string + "&" + urlencode_rfc3986(k) + "=" + urlencode_rfc3986(d[k])
  else:
    canonical_string = canonical_string[1:]

  return canonical_string

def create_request_to_amazon_url(d):
  canonical_string = create_canonical_string(d)
  parsed_url = urlparse(amazon_api_product_advertising_request_url)
  string_to_sign = "GET\n" + parsed_url.hostname + "\n" + parsed_url.path +"\n" + canonical_string
  signature = hmac.new(amazon_api_secret_access_key, string_to_sign, hashlib.sha256).digest()
  signature = base64.b64encode(signature)
  url = amazon_api_product_advertising_request_url + "?" + canonical_string + "&Signature=" + urlencode_rfc3986(signature)
  return url

呼び出しは下のような形でコール

#!/usr/bin/env python
#
# Copyright 2007 Google Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
import webapp2
import jinja2
import constants
import datetime
from google.appengine.api import urlfetch
from xml.etree import ElementTree


class BrowseNodeLookupHandler(webapp2.RequestHandler):
  def get(self):
    self.response.headers['Content-Type'] = 'text/html'

    params = {}
    params["Service"] = constants.amazon_api_service
    params["AWSAccessKeyId"] = constants.amazon_api_access_key_id
    params["AssociateTag"] = constants.amazon_api_associatetag
    params["Operation"] = constants.amazon_api_browsenodelookup
    params["Timestamp"] = datetime.datetime.utcnow().strftime("%Y-%m-%dT%H:%M:%SZ")
    params["BrowseNodeId"] = constants.amazon_api_browsenode_apparel

    url = constants.create_request_to_amazon_url(params)
    result = urlfetch.fetch(url)
    if result.status_code == 200:
      xmlTree = ElementTree.fromstring(result)
      

app = webapp2.WSGIApplication([
  ('/search/browsenodelookup', BrowseNodeLookupHandler)
], debug=True)

BrowseNodeLookupは、ロケールによって値が変わるのでそこは注意をする必要がある。