update explainParams with test

Author: mengxr

mllib/src/test/scala/org/apache/spark/ml/param/TestParams.scala

@@ -17,16 +17,13 @@
 
 package org.apache.spark.ml.param
 
+import org.apache.spark.ml.param.shared.{HasInputCol, HasMaxIter}
+
 /** A subclass of Params for testing. */
-class TestParams extends Params {
+class TestParams extends Params with HasMaxIter with HasInputCol {
 
-  val maxIter = new IntParam(this, "maxIter", "max number of iterations")
   def setMaxIter(value: Int): this.type = { set(maxIter, value); this }
-  def getMaxIter: Int = getOrDefault(maxIter)
-
-  val inputCol = new Param[String](this, "inputCol", "input column name")
   def setInputCol(value: String): this.type = { set(inputCol, value); this }
-  def getInputCol: String = getOrDefault(inputCol)
 
   setDefault(maxIter -> 10)
 

python/pyspark/ml/param/__init__.py

@@ -75,12 +75,12 @@ def _explain(self, param):
         values = []
         if self.isDefined(param):
             if self.defaultParamMap.has_key(param):
-                values += "default: %s" % self.defaultParamMap[param]
+                values.append("default: %s" % self.defaultParamMap[param])
             if self.paramMap.has_key(param):
-                values += "current: %s" % self.paramMap[param]
+                values.append("current: %s" % self.paramMap[param])
         else:
-            values += "undefined"
-        valueStr = "(" + ",".join(values) + ")"
+            values.append("undefined")
+        valueStr = "(" + ", ".join(values) + ")"
         return "%s: %s %s" % (param.name, param.doc, valueStr)
 
     def explainParams(self):

python/pyspark/ml/tests.py

@@ -153,6 +153,10 @@ def test_params(self):
         with self.assertRaises(KeyError):
             testParams.getInputCol()
 
+        self.assertEquals(testParams.explainParams(),
+            "\n".join(["inputCol: input column name (undefined)",
+                       "maxIter: max number of iterations (default: 10, current: 100)"]))
+
 
 if __name__ == "__main__":
     unittest.main()