Ask Ben: Screen Scraping PowerBall Statistics With ColdFusion
Posted January 14, 2008 at 8:15 AM
I was spending my free time this weekend checking the powerball website when i decided i wanted to use cfhttp and get the number frequency information on this page:
http://www.powerball.com/powerball/pb_frequency.asp?
matrixID=2&graph=0
The problem is I am not sure what to do next.
What I am trying to do is get into this page and grab the numbers from the table...then loop through a DB insert and populate a table. How do I do this using cfhttp?
Before we get into this, let's just talk about screen scraping for a second. Screen scraping is always a dangerous thing to do because it relies on a third-party service that may change at the drop of a hat. When scowering a page for data, we can do things like search for keywords and match patterns, which works; but, at any time, the target page can have its structure change which may or may not render our algorithm completely useless. So, use screen scraping with discretion.
That being said, let's dive right into the problem. While I don't know what database you are going to use to store the PowerBall statistics, I am going to move the PowerBall data into a manually created ColdFusion query. You can then easily take this ColdFusion query, loop over it, and insert the values into a database.
In order to get the PowerBall statistical data from the page, we are going to use a little regular expression pattern matching. From looking at the page source of the given URL, it is clear that the PowerBall statistics exist in an HTML table with set headers. We can use this knowledge to pull out every complete table and search its contents for the given headers. This will give us a sort of brute force way to find the proper data table.
Once we have this HTML data table in a variable, we are going to treat it like an XML document against which we can run some XmlSearch() calls. The hurdle with this is that most HTML is not really XML-standards compliant. So, to get around this, we are going to take our table HTML and try to strip out all elements and attributes that might violate XML standards. This will include all the Font tags and Br tags and even the table tag attributes. Once this is done, we should be left with a data string that consists only of table, tr, and td tags which can easily be parsed.
Let's take a look at that code:
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- <!---
- Determine the PowerBall URL that we want to scrape.
- NOTE: I am building this rather than just putting it
- in the CFHttp tag for text-wrapping reasons.
- --->
- <cfset strURL = (
- "http://www.powerball.com/powerball/pb_frequency.asp?" &
- "matrixID=2&graph=0"
- ) />
-
-
- <!--- Grab the PowerBall HTML page. --->
- <cfhttp
- url="#strURL#"
- method="get"
- useragent="#CGI.http_user_agent#"
- result="objGet"
- />
-
-
- <!---
- We want to grab all the tables out of the page.
- One of them should be the one that we are looking for.
- Realize, however, that we are doing this based on what
- the HTML of the target page looked like at the time of
- this writing. One of the dangerous parts of screen
- scraping is that the target page may change at any time
- without any warning, rendering this algorithm totally
- useless.
- --->
- <cfset objPattern = CreateObject(
- "java",
- "java.util.regex.Pattern"
- ).Compile(
- JavaCast(
- "string",
- "(?i)<table[^>]*>([\w\W](?!<table))+?</table>"
- )
- ) />
-
-
- <!---
- Create the pattern matcher based on our regular
- expression pattern and the FileContent that we got
- from our CFHttp call.
- --->
- <cfset objMatcher = objPattern.Matcher(
- JavaCast( "string", objGet.FileContent )
- ) />
-
-
- <!---
- Set default table code. This variable will hopefully
- contain our target HTML table in a little bit.
- --->
- <cfset strTableHtml = "" />
-
-
- <!--- Find the proper table. --->
- <cfloop condition="objMatcher.Find()">
-
- <!---
- Check to see if we have the right table. This
- one will contain the header values taht we are
- searching for.
-
- NOTE: Just a reminder that this may change at any
- point and only holds true at the time that this
- blog entry was written.
- --->
- <cfif (
- Find( "Ball Number", objMatcher.Group() ) AND
- Find( "White Balls", objMatcher.Group() ) AND
- Find( "Powerball", objMatcher.Group() ) AND
- Find( "Power Play", objMatcher.Group() )
- )>
-
- <!--- Extract table code. --->
- <cfset strTableHtml = objMatcher.Group() />
-
- </cfif>
-
- </cfloop>
-
-
- <!--- Check to see if we have found the HTML table. --->
- <cfif Len( strTableHtml )>
-
- <!---
- Now that we have the table HTML, we want to
- strip out most of the data so that we can treat
- it as XHTML. To do this, we are going to strip out
- everything but the table related tags.
- --->
- <cfset strTableHtml = strTableHtml.ReplaceAll(
- JavaCast( "string", "(?i)<(?!/?(ta|tr|th|td))[^>]*>" ),
- JavaCast( "string", " " )
- ) />
-
-
- <!---
- Now, strip out all tag attributes. This just helps
- to make sure that the resultant HTML is more likely
- to stick to an XML standard.
- --->
- <cfset strTableHtml = strTableHtml.ReplaceAll(
- JavaCast( "string", "(?i)<(/?\w+)[^>]*>" ),
- JavaCast( "string", "<$1>" )
- ) />
-
-
- <!---
- ASSERT: At this point, the XHTML that we have
- remaining should function as a basic XML document,
- which we can query off of.
- --->
-
-
- <!---
- Now, let's build a ColdFusion query that will hold
- the values of the HTML.
- --->
- <cfset qPowerBall = QueryNew(
- "ball_number, white_ball_fr, powerball_fr, power_play_fr",
- "varchar, varchar, varchar, varchar"
- ) />
-
-
- <!---
- Get all TR elements that are in the 3rd or greater
- position (we have no need to grab the headers or
- the buffer row that exists between the header and
- the body rows).
- --->
- <cfset arrTR = XmlSearch(
- Trim( strTableHtml ),
- "//tr[ position() > 2 ]"
- ) />
-
-
- <!--- Loop over the TR nodes. --->
- <cfloop
- index="intTRIndex"
- from="1"
- to="#ArrayLen( arrTR )#"
- step="1">
-
- <!---
- Get a short hand reference for the current
- TR node.
- --->
- <cfset xmlTR = arrTR[ intTRIndex ] />
-
-
- <!---
- For each row, we are going to want to add a record
- the PowerBall query we are building.
- --->
- <cfset QueryAddRow( qPowerBall ) />
-
-
- <!---
- For each row, we might have anywhere from zero to
- four columns. We won't know until we query for the
- TD text. When querying for text, we want to make
- sure to strip out the white space which we may have
- created when cleaning the HTML. Normally, we would
- use normalize-space() to trim the text() value, but
- CFMX7 does not support this yet.
- --->
- <cfset arrTD = XmlSearch(
- xmlTR,
- "td/text()"
- ) />
-
-
- <!--- Loop over the TD values. --->
- <cfloop
- index="intTDIndex"
- from="1"
- to="#ArrayLen( arrTD )#"
- step="1">
-
- <!---
- The column to which we add this value will
- depend on the index of the current TD.
- --->
- <cfswitch expression="#intTDIndex#">
- <cfcase value="1">
- <cfset strColumn = "ball_number" />
- </cfcase>
- <cfcase value="2">
- <cfset strColumn = "white_ball_fr" />
- </cfcase>
- <cfcase value="3">
- <cfset strColumn = "powerball_fr" />
- </cfcase>
- <cfcase value="4">
- <cfset strColumn = "power_play_fr" />
- </cfcase>
- </cfswitch>
-
-
- <!---
- Set the column value. Be sure to cast to a Java
- String, just to make sure we don't corrupt our
- ColdFusion query.
- --->
- <cfset qPowerBall[ strColumn ][ qPowerBall.RecordCount ] = JavaCast( "string", Trim( arrTD[ intTDIndex ].XmlValue ) ) />
-
- </cfloop>
-
- </cfloop>
-
-
- <!--- Dump out the resultant query. --->
- <cfdump
- var="#qPowerBall#"
- label="PowerBall Statistics"
- />
-
- </cfif>
Running the code, we get the following PowerBall statistics query:
| | | | ||
| |  | | ||
| | | |
Works quite nicely. Just remember, the cell values in our ColdFusion query that look like empty strings are actually NULL values, but ColdFusion will treat them as empty strings. When you go to insert these values into your own database, you can either use the null="" attribute of the CFQueryParam tag to insert the nulls, or just use the column value (qPowerBall.COLUMN) to insert an empty string.
Hope that helps a bit.
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Reader Comments
Thanks Ben, this is awesome...I'm going to work with it want I get home.
Frank
@Frank,
My pleasure.
Ben, I have a mildly retarded question. How do I stuff the output into an access table? I don't even know what angle to come from at this (laugh).
@Frank,
No problem. All you have to do is loop over the resultant PowerBall query and insert each record. Something like this:
<cfloop query="qPowerBall">
<cfquery name="qInsert" datasource="...">
INSERT INTO pb
(
ball_number,
frequency
) VALUES (
<cfquerypara value="#qPowerBall.ball_number#" type="cf_sql_varchar" />,
<cfquerypara value="#qPowerBall.powerball_fr#" type="cf_sql_varchar" />
);
</cfquery>
</cfloop>
Of course, you just need to adjust for the columns that you actually have. Should be good.
Thanks again Ben. I'll give that a go when I get home.
Now, how about a probability algorithm based on the ball drop frequency?
HA! just kidding...
:D
Thanks Again...
Just copy and paste into excel. Run your stats then.
When attempting to test the code provided on my host, I get an error stating "...denied access to createobject(java)..."
What is the (or a ) workaround for this?
Thank you,
John
@John,
Sounds like the CreateObject() method is not allowed in your hosting environment. You might want to try CFInvoke, but to be honest, I am not sure if that can create Java objects (I hardly ever use it).
it's so many things that I can learn from here... great
keep updating....
Thanks Ben for pointing me to this thread - this looks exactly like what I could use!
This site is übercool... I should take a week off and do nothing but read up on all the great advice and become a better programmer :-)
@Jonas,
Ha ha, thanks for the kind words. Glad to be helping.
I am using your code and works great btw. My question is, this pulls the first table which is correct, but this table is within a td cell and I need to pull 5 more cells in this row and this continues on for 2 more rows. So to sum, you have a table with 16 cells. I need the table within each cell. Is this even possible lol?
