SPARK-977 Added Python RDD.zip function

was raised earlier as a part of  apache/incubator-spark#486

Author: Prabin Banka <prabin.banka@imaginea.com>

Closes #76 from prabinb/python-api-zip and squashes the following commits:

b1a31a0 [Prabin Banka] Added Python RDD.zip function

1 files changed, 28 insertions, 1 deletions

diff --git a/python/pyspark/serializers.py b/python/pyspark/serializers.py
index 8c6ad79059..12c63f186a 100644
--- a/python/pyspark/serializers.py
+++ b/python/pyspark/serializers.py
@@ -204,7 +204,7 @@ class CartesianDeserializer(FramedSerializer):
         self.key_ser = key_ser
         self.val_ser = val_ser
 
-    def load_stream(self, stream):
+    def prepare_keys_values(self, stream):
         key_stream = self.key_ser._load_stream_without_unbatching(stream)
         val_stream = self.val_ser._load_stream_without_unbatching(stream)
         key_is_batched = isinstance(self.key_ser, BatchedSerializer)
@@ -212,6 +212,10 @@ class CartesianDeserializer(FramedSerializer):
         for (keys, vals) in izip(key_stream, val_stream):
             keys = keys if key_is_batched else [keys]
             vals = vals if val_is_batched else [vals]
+            yield (keys, vals)
+
+    def load_stream(self, stream):
+        for (keys, vals) in self.prepare_keys_values(stream):
             for pair in product(keys, vals):
                 yield pair
 
@@ -224,6 +228,29 @@ class CartesianDeserializer(FramedSerializer):
                (str(self.key_ser), str(self.val_ser))
 
 
+class PairDeserializer(CartesianDeserializer):
+    """
+    Deserializes the JavaRDD zip() of two PythonRDDs.
+    """
+
+    def __init__(self, key_ser, val_ser):
+        self.key_ser = key_ser
+        self.val_ser = val_ser
+
+    def load_stream(self, stream):
+        for (keys, vals) in self.prepare_keys_values(stream):
+            for pair in izip(keys, vals):
+                yield pair
+
+    def __eq__(self, other):
+        return isinstance(other, PairDeserializer) and \
+               self.key_ser == other.key_ser and self.val_ser == other.val_ser
+
+    def __str__(self):
+        return "PairDeserializer<%s, %s>" % \
+               (str(self.key_ser), str(self.val_ser))
+
+
 class NoOpSerializer(FramedSerializer):
 
     def loads(self, obj): return obj