Add notes to python documentation about using SparkContext.setSystemProperty.

docs/python-programming-guide.md

@@ -131,6 +131,17 @@ sc = SparkContext("local", "App Name", pyFiles=['MyFile.py', 'lib.zip', 'app.egg
 Files listed here will be added to the `PYTHONPATH` and shipped to remote worker machines.
 Code dependencies can be added to an existing SparkContext using its `addPyFile()` method.
 
+You can set [system properties](configuration.html#system-properties)
+using `SparkContext.setSystemProperty()` class method *before*
+instantiating SparkContext. For example, to set the amount of memory
+per executor process:
+
+{% highlight python %}
+from pyspark import SparkContext
+SparkContext.setSystemProperty('spark.executor.memory', '2g')
+sc = SparkContext("local", "App Name")
+{% endhighlight %}
+
 # API Docs
 
 [API documentation](api/pyspark/index.html) for PySpark is available as Epydoc.