Amazon Web Services Support

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Front Matter

Copyright (c) 2003 Dave Kuhlman

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Abstract:

Contents

• Front Matter
• 1. Introduction
  • 1.1 What It Does
  • 1.2 What Is Included
• 2. How-to Use It
  • 2.1 Try it out
  • 2.2 Creating sub-classes
  • 2.3 Creating an application/harness
  • 2.4 The parsing functions
    • 2.4.1 parse(inFileName)
    • 2.4.2 parseString(aString)
• End Matter
  • Acknowledgements and Thanks
• About this document ...

 
1. Introduction

This document describes additional support for developing Python access to Amazon WS (Amazon Web services). This support is usable with the "XML over HTTP" style of Amazon WS, which is mostly REST-like.

A distribution file containing this support is at amazon_ws_support-1.0.tar.gz.

This support provides modules containing classes that represent the content of the response to a request to Amazon Web services. These modules are also capable of parsing the response XML document.

This support is intended to be used with the XML over HTTP approach to Amazon Web services. One module is provided for the "lite" response document and another module is provided for the "heavy" response document.

The support modules were initially generated with generateDS.py. A copy of generateDS.py is included with the distribution. You can learn more about generateDS.py at http://www.rexx.com/~dkuhlman/#generateDS.

The distribution also includes a very small, example application get_books.py that uses the support modules.

1.1 What It Does

The parser -- Parses an Amazon Web service response document and creates instances of the representation classes. The support modules (dev_lite_sup.py and dev_lite_sub.py, for example) contain functions parse(inFilename) and parseString(inString).

The super-classes -- These are the representation classes. They provide getter and setter functions for member variables, a function (build) to build an instance from the corresponding DOM object, and export function (export).

The sub-classes -- These sub-classes of the representation classes are where you hang your code.

The source code generator -- A copy of generateDS.py is included. This can be used to re-generate the XML representation classes from the XML Schema documents, which are also included.

1.2 What Is Included

• Sample (instance) XML documents from the Amazon WS kit:
  • amazon-exchange-item-Search.xml

  • amazon-seller-profile.xml

  • amazon-seller-search.xml

  • amazon-used-product-search.xml

  • webserv-example-heavy.xml

  • webserv-example-lite.xml

  • webserv-example2-heavy.xml

• XML Schema files generated from the above instance XML documents using generateXsd.py:
  • amazon-exchange-item-Search.xsd

  • amazon-seller-profile.xsd

  • amazon-seller-search.xsd

  • amazon-used-product-search.xsd

  • webserv-example-heavy.xsd

  • webserv-example-lite.xsd

  • webserv-example2-heavy.xsd

• The Python modules generated from the XML Schema documents by generateDS.py which can be used to parse and represent the content of instance XML documents:
  • amazon_exchange_item_Search_sub.py

  • amazon_exchange_item_Search_sup.py

  • amazon_seller_profile_sub.py

  • amazon_seller_profile_sup.py

  • amazon_seller_search_sub.py

  • amazon_seller_search_sup.py

  • amazon_used_product_search_sub.py

  • amazon_used_product_search_sup.py

  • webserv_example2_heavy_sub.py

  • webserv_example2_heavy_sup.py

  • webserv_example_heavy_sub.py

  • webserv_example_heavy_sup.py

  • webserv_example_lite_sub.py

  • webserv_example_lite_sup.py

• get_books.py -- A test harness that uses webserv_example_lite_sub and webserv_example_heavy_sub to make keyword requests for lists of books and display the results.

• generateXsd.py -- A program used to generate the XML Schema documents from the sample XML instance documents. Caution: This program has limitations. It may generate XML Schemas that are not complete, in particular, if not all elements are present in the the sample XML instance document. And, generateXsd.py is not particularly good at picking up the minoccurs and maxoccurs attributes. Some editing of the generated XML Schema documents is required.

• generateDS.py -- A program used to generate the Python modules from the XML Schema documents. generateDS.py is also available separately. More information is at http://www.rexx.com/~dkuhlman/#generateDS.

 
2. How-to Use It

2.1 Try it out

Try this test:

python get_books.py -a [my_amazon_dev_token] pruning tree

2.2 Creating sub-classes

You can create a new (empty) sub-class file with the either of the following:

./generateDS.py -s my_lite_sub.py dev-lite.xsd
./generateDS.py -s my_heavy_sub.py dev-heavy.xsd

Why would you want to do this? You can, for example, create a new sub-class file, then "decorate" the classes in it with methods that perform specialized tasks.

2.3 Creating an application/harness

There is a example in get_books.py.

How to do it:

1. Create a module containing the sub-classes. Use either of the following depending on which response document type you intend to request:

   ./generateDS.py -s mysubclasses.py dev-lite.xsd
   ./generateDS.py -s mysubclasses.py dev-heavy.xsd
   

2. Decorate the classes in the sub-class module with your application specific behaviors. For example, here is what you might add to mysubclasses.py:

   class ProductInfoSub(supermod.ProductInfo):
       o
       o
       o
       def showProduct(self):
           for detail in self.getDetails():
               detail.showProduct(count)
   supermod.ProductInfo.subclass = ProductInfoSub
   # end class ProductInfoSub
   
   class DetailsSub(supermod.Details):
       o
       o
       o
       def showProduct(self, count):
           name = self.getProductname()
           print '%d. ProductName: %s' % (count, name)
           authors = self.getAuthors()
           if authors:
               authors = authors.getAuthor()
               print 'Authors:'
               for author in authors:
                   print '    %s' % author
           price = self.getOurprice()
           if price:
               print 'Price: %s' % price
           else:
               print 'Price not available'
   supermod.Details.subclass = DetailsSub
   # end class DetailsSub
   

3. In your application, import the module. For example:

   import mysubclasses
   

4. Parse the document and call the specialized method in the root object. Here is a simple example of how to do so:

   import mysubclasses
   import urllib
   
   f = urllib.urlopen(url)
   content = f.read()
   f.close()
   doc = mysubclasses.parseString(content)
   doc.showProduct()
   

2.4 The parsing functions

The support modules contain functions that parse an XML document returned by a request to Amazon WS. These functions return an instance of the root object, an instance of class ProductInfo.

2.4.1 parse(inFileName)

Usage:

import dev_lite_sub
root = dev_lite_sub.parse(inFileName)

Or:

import dev_heavy_sub
root = dev_heavy_sub.parse(inFileName)

Where:

• inFileName is the name of a file containing the XML document returned from a request to Amazon WS.

Returns -- An instance of class ProductInfo.

2.4.2 parseString(aString)

Usage:

import dev_lite_sub
root = dev_lite_sub.parseString(aString)

Or:

import dev_heavy_sub
root = dev_heavy_sub.parseString(aString)

Where:

• aString is a string containing the XML document returned from a request to Amazon WS.

Returns -- An instance of class ProductInfo.

 
End Matter

Acknowledgements and Thanks

Thanks to Amazon for the Amazon Web Services API and Web Services toolkit.

About this document ...

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Amazon Web Services Support

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Release 1.00, documentation updated on April 16, 2003.