So what you want to do here is read the photocell voltage as a digital value.  The circuit is really just an RC circuit that allows you to "measure" the resistance of the photocell as a digital value. 

Since you are measuring you'll want to configure pin 23 as "Input".

Then you just want to do a series of readings. In the WolframLanguage, we have a function that helps you do just that.

DeviceReadTimeSeries["GPIO",{1,0.1}, 23]

will read pin 23 for 1 second at an interval of 0.1 seconds.

Check it out!

http://reference.wolfram.com/language/ref/DeviceReadTimeSeries.html

Using this, you should be able to analyze the time series and figure out the resistance.

Or if you want to try to write code similar to the python example, you can use DeviceRead instead.  This will give you a single reading.  You can put this in your own loop then.