Add posexplode to python

Author: dongjoon-hyun

python/pyspark/sql/functions.py

@@ -1637,6 +1637,27 @@ def explode(col):
     return Column(jc)
 
 
+@since(2.1)
+def posexplode(col):
+    """Returns a new row for each element with position in the given array or map.
+
+    >>> from pyspark.sql import Row
+    >>> eDF = spark.createDataFrame([Row(a=1, intlist=[1,2,3], mapfield={"a": "b"})])
+    >>> eDF.select(posexplode(eDF.intlist)).collect()
+    [Row(pos=0, col=1), Row(pos=1, col=2), Row(pos=2, col=3)]
+
+    >>> eDF.select(posexplode(eDF.mapfield)).show()
+    +---+---+-----+
+    |pos|key|value|
+    +---+---+-----+
+    |  0|  a|    b|
+    +---+---+-----+
+    """
+    sc = SparkContext._active_spark_context
+    jc = sc._jvm.functions.posexplode(_to_java_column(col))
+    return Column(jc)
+
+
 @ignore_unicode_prefix
 @since(1.6)
 def get_json_object(col, path):