[SPARK-8116][PYSPARK] Allow sc.range() to take a single argument.

Author: Ted Blackman <ted.blackman@gmail.com>

Closes #6656 from belisarius222/branch-1.4 and squashes the following commits:

747cbc2 [Ted Blackman] [SPARK-8116][PYSPARK] Allow sc.range() to take a single argument.

python/pyspark/context.py

@@ -324,10 +324,12 @@ class SparkContext(object):
         with SparkContext._lock:
             SparkContext._active_spark_context = None
 
-    def range(self, start, end, step=1, numSlices=None):
+    def range(self, start, end=None, step=1, numSlices=None):
         """
         Create a new RDD of int containing elements from `start` to `end`
-        (exclusive), increased by `step` every element.
+        (exclusive), increased by `step` every element. Can be called the same
+        way as python's built-in range() function. If called with a single argument,
+        the argument is interpreted as `end`, and `start` is set to 0.
 
         :param start: the start value
         :param end: the end value (exclusive)
@@ -335,9 +337,17 @@ class SparkContext(object):
         :param numSlices: the number of partitions of the new RDD
         :return: An RDD of int
 
+        >>> sc.range(5).collect()
+        [0, 1, 2, 3, 4]
+        >>> sc.range(2, 4).collect()
+        [2, 3]
         >>> sc.range(1, 7, 2).collect()
         [1, 3, 5]
         """
+        if end is None:
+            end = start
+            start = 0
+
         return self.parallelize(xrange(start, end, step), numSlices)
 
     def parallelize(self, c, numSlices=None):