12.7. Searching Google

Let's finally turn to the sample code that you saw that the beginning of this chapter, which does something more useful and exciting than get the current temperature.

Google provides a SOAP API for programmatically accessing Google search results. To use it, you will need to sign up for Google Web Services.

Procedure 12.4. Signing Up for Google Web Services

  1. Go to http://www.google.com/apis/ and create a Google account. This requires only an email address. After you sign up you will receive your Google API license key by email. You will need this key to pass as a parameter whenever you call Google's search functions.

  2. Also on http://www.google.com/apis/, download the Google Web APIs developer kit. This includes some sample code in several programming languages (but not Python), and more importantly, it includes the WSDL file.

  3. Decompress the developer kit file and find GoogleSearch.wsdl. Copy this file to some permanent location on your local drive. You will need it later in this chapter.

Once you have your developer key and your Google WSDL file in a known place, you can start poking around with Google Web Services.

Example 12.12. Introspecting Google Web Services

>>> from SOAPpy import WSDL
>>> server = WSDL.Proxy('/path/to/your/GoogleSearch.wsdl') 1
>>> server.methods.keys()                                  2
[u'doGoogleSearch', u'doGetCachedPage', u'doSpellingSuggestion']
>>> callInfo = server.methods['doGoogleSearch']
>>> for arg in callInfo.inparams:                          3
...     print arg.name.ljust(15), arg.type
key             (u'http://www.w3.org/2001/XMLSchema', u'string')
q               (u'http://www.w3.org/2001/XMLSchema', u'string')
start           (u'http://www.w3.org/2001/XMLSchema', u'int')
maxResults      (u'http://www.w3.org/2001/XMLSchema', u'int')
filter          (u'http://www.w3.org/2001/XMLSchema', u'boolean')
restrict        (u'http://www.w3.org/2001/XMLSchema', u'string')
safeSearch      (u'http://www.w3.org/2001/XMLSchema', u'boolean')
lr              (u'http://www.w3.org/2001/XMLSchema', u'string')
ie              (u'http://www.w3.org/2001/XMLSchema', u'string')
oe              (u'http://www.w3.org/2001/XMLSchema', u'string')
1 Getting started with Google web services is easy: just create a WSDL.Proxy object and point it at your local copy of Google's WSDL file.
2 According to the WSDL file, Google offers three functions: doGoogleSearch, doGetCachedPage, and doSpellingSuggestion. These do exactly what they sound like: perform a Google search and return the results programmatically, get access to the cached version of a page from the last time Google saw it, and offer spelling suggestions for commonly misspelled search words.
3 The doGoogleSearch function takes a number of parameters of various types. Note that while the WSDL file can tell you what the arguments are called and what datatype they are, it can't tell you what they mean or how to use them. It could theoretically tell you the acceptable range of values for each parameter, if only specific values were allowed, but Google's WSDL file is not that detailed. WSDL.Proxy can't work magic; it can only give you the information provided in the WSDL file.

Here is a brief synopsis of all the parameters to the doGoogleSearch function:

Example 12.13. Searching Google

>>> from SOAPpy import WSDL
>>> server = WSDL.Proxy('/path/to/your/GoogleSearch.wsdl')
>>> results = server.doGoogleSearch(key, 'mark', 0, 10, False, "",
...     False, "", "utf-8", "utf-8")             1
>>> len(results.resultElements)                  2
>>> results.resultElements[0].URL                3
>>> results.resultElements[0].title
'dive into <b>mark</b>'
1 After setting up the WSDL.Proxy object, you can call server.doGoogleSearch with all ten parameters. Remember to use your own Google API key that you received when you signed up for Google web services.
2 There's a lot of information returned, but let's look at the actual search results first. They're stored in results.resultElements, and you can access them just like a normal Python list.
3 Each element in the resultElements is an object that has a URL, title, snippet, and other useful attributes. At this point you can use normal Python introspection techniques like dir(results.resultElements[0]) to see the available attributes. Or you can introspect through the WSDL proxy object and look through the function's outparams. Each technique will give you the same information.

The results object contains more than the actual search results. It also contains information about the search itself, such as how long it took and how many results were found (even though only 10 were returned). The Google web interface shows this information, and you can access it programmatically too.

Example 12.14. Accessing Secondary Information From Google

>>> results.searchTime                     1
>>> results.estimatedTotalResultsCount     2
>>> results.directoryCategories            3
[<SOAPpy.Types.structType item at 14367400>:
  'specialEncoding': ''}]
>>> results.directoryCategories[0].fullViewableName
1 This search took 0.224919 seconds. That does not include the time spent sending and receiving the actual SOAP XML documents. It's just the time that Google spent processing your request once it received it.
2 In total, there were approximately 30 million results. You can access them 10 at a time by changing the start parameter and calling server.doGoogleSearch again.
3 For some queries, Google also returns a list of related categories in the Google Directory. You can append these URLs to http://directory.google.com/ to construct the link to the directory category page.