[SPARK-13047][PYSPARK][ML] Pyspark Params.hasParam should not throw a…

…n error

Pyspark Params class has a method `hasParam(paramName)` which returns `True` if the class has a parameter by that name, but throws an `AttributeError` otherwise. There is not currently a way of getting a Boolean to indicate if a class has a parameter. With Spark 2.0 we could modify the existing behavior of `hasParam` or add an additional method with this functionality.

In Python:
```python
from pyspark.ml.classification import NaiveBayes
nb = NaiveBayes()
print nb.hasParam("smoothing")
print nb.hasParam("notAParam")
```
produces:
> True
> AttributeError: 'NaiveBayes' object has no attribute 'notAParam'

However, in Scala:
```scala
import org.apache.spark.ml.classification.NaiveBayes
val nb  = new NaiveBayes()
nb.hasParam("smoothing")
nb.hasParam("notAParam")
```
produces:
> true
> false

cc holdenk

Author: sethah <[email protected]>

Closes #10962 from sethah/SPARK-13047.

(cherry picked from commit b354673)
Signed-off-by: Xiangrui Meng <[email protected]>

python/pyspark/ml/param/__init__.py

@@ -156,8 +156,11 @@ def hasParam(self, paramName):
         Tests whether this instance contains a param with a given
         (string) name.
         """
-        param = self._resolveParam(paramName)
-        return param in self.params
+        if isinstance(paramName, str):
+            p = getattr(self, paramName, None)
+            return isinstance(p, Param)
+        else:
+            raise TypeError("hasParam(): paramName must be a string")
 
     @since("1.4.0")
     def getOrDefault(self, param):

python/pyspark/ml/tests.py

@@ -170,6 +170,11 @@ def test_param(self):
         self.assertEqual(maxIter.doc, "max number of iterations (>= 0).")
         self.assertTrue(maxIter.parent == testParams.uid)
 
+    def test_hasparam(self):
+        testParams = TestParams()
+        self.assertTrue(all([testParams.hasParam(p.name) for p in testParams.params]))
+        self.assertFalse(testParams.hasParam("notAParameter"))
+
     def test_params(self):
         testParams = TestParams()
         maxIter = testParams.maxIter
@@ -179,7 +184,7 @@ def test_params(self):
         params = testParams.params
         self.assertEqual(params, [inputCol, maxIter, seed])
 
-        self.assertTrue(testParams.hasParam(maxIter))
+        self.assertTrue(testParams.hasParam(maxIter.name))
         self.assertTrue(testParams.hasDefault(maxIter))
         self.assertFalse(testParams.isSet(maxIter))
         self.assertTrue(testParams.isDefined(maxIter))
@@ -188,7 +193,7 @@ def test_params(self):
         self.assertTrue(testParams.isSet(maxIter))
         self.assertEqual(testParams.getMaxIter(), 100)
 
-        self.assertTrue(testParams.hasParam(inputCol))
+        self.assertTrue(testParams.hasParam(inputCol.name))
         self.assertFalse(testParams.hasDefault(inputCol))
         self.assertFalse(testParams.isSet(inputCol))
         self.assertFalse(testParams.isDefined(inputCol))