[SPARK-14605][ML][PYTHON] Changed Python to use unicode UIDs for spar…

…k.ml Identifiable

## What changes were proposed in this pull request?

Python spark.ml Identifiable classes use UIDs of type str, but they should use unicode (in Python 2.x) to match Java. This could be a problem if someone created a class in Java with odd unicode characters, saved it, and loaded it in Python.

This PR: Use unicode everywhere in Python.

## How was this patch tested?

Updated persistence unit test to check uid type

Author: Joseph K. Bradley <joseph@databricks.com>

Closes #12368 from jkbradley/python-uid-unicode.

python/pyspark/ml/param/__init__.py

@@ -485,10 +485,11 @@ def _resetUid(self, newUid):
         Changes the uid of this instance. This updates both
         the stored uid and the parent uid of params and param maps.
         This is used by persistence (loading).
-        :param newUid: new uid to use
+        :param newUid: new uid to use, which is converted to unicode
         :return: same instance, but with the uid and Param.parent values
                  updated, including within param maps
         """
+        newUid = unicode(newUid)
         self.uid = newUid
         newDefaultParamMap = dict()
         newParamMap = dict()

python/pyspark/ml/tests.py

@@ -621,6 +621,8 @@ def test_linear_regression(self):
         lr_path = path + "/lr"
         lr.save(lr_path)
         lr2 = LinearRegression.load(lr_path)
+        self.assertEqual(lr.uid, lr2.uid)
+        self.assertEqual(type(lr.uid), type(lr2.uid))
         self.assertEqual(lr2.uid, lr2.maxIter.parent,
                          "Loaded LinearRegression instance uid (%s) did not match Param's uid (%s)"
                          % (lr2.uid, lr2.maxIter.parent))

python/pyspark/ml/util.py

@@ -21,6 +21,7 @@
 
 if sys.version > '3':
     basestring = str
+    unicode = str
 
 from pyspark import SparkContext, since
 from pyspark.mllib.common import inherit_doc
@@ -67,10 +68,10 @@ def __repr__(self):
     @classmethod
     def _randomUID(cls):
         """
-        Generate a unique id for the object. The default implementation
+        Generate a unique unicode id for the object. The default implementation
         concatenates the class name, "_", and 12 random hex chars.
         """
-        return cls.__name__ + "_" + uuid.uuid4().hex[12:]
+        return unicode(cls.__name__ + "_" + uuid.uuid4().hex[12:])
 
 
 @inherit_doc

python/pyspark/ml/wrapper.py

@@ -254,7 +254,7 @@ def __init__(self, java_model=None):
         """
         super(JavaModel, self).__init__(java_model)
         if java_model is not None:
-            self.uid = java_model.uid()
+            self._resetUid(java_model.uid())
 
     def copy(self, extra=None):
         """