Github user jkbradley commented on a diff in the pull request:
https://github.com/apache/spark/pull/11663#discussion_r57024858
--- Diff: python/pyspark/ml/param/__init__.py ---
@@ -65,6 +75,146 @@ def __eq__(self, other):
return False
+class TypeConverters(object):
+ """
+ .. note:: DeveloperApi
+
+ Factory methods for common type conversion functions for
`Param.typeConverter`.
+
+ .. versionadded:: 2.0.0
+ """
+
+ @staticmethod
+ def _is_numeric(value):
+ vtype = type(value)
+ return vtype in [int, float, np.float64, np.int64] or
vtype.__name__ == 'long'
+
+ @staticmethod
+ def _is_integer(value):
+ if TypeConverters._is_numeric(value):
+ value = float(value)
+ return value.is_integer()
+ else:
+ return False
+
+ @staticmethod
+ def _can_convert_to_list(value):
+ vtype = type(value)
+ return vtype == list or vtype == np.ndarray or isinstance(value,
Vector)
+
+ @staticmethod
+ def _is_string(value):
+ vtype = type(value)
+ return vtype in [str, np.unicode_, np.string_, np.str_] or
type(value).__name__ == 'unicode'
+
+ @staticmethod
+ def identity(value):
+ """
+ Dummy converter that just returns value.
+ """
+ return value
+
+ @staticmethod
+ def toList(value):
+ """
+ Convert a value to a list, if possible.
+ """
+ if type(value) == list:
+ return value
+ elif type(value) == np.ndarray:
+ return list(value)
+ elif isinstance(value, Vector):
+ return list(value.toArray())
+ else:
+ raise TypeError("Could not convert %s to list" % value)
+
+ @staticmethod
+ def toListFloat(value):
+ """
+ Convert a value to list of floats, if possible.
+ """
+ if TypeConverters._can_convert_to_list(value):
+ value = TypeConverters.toList(value)
+ if all(map(lambda v: TypeConverters._is_numeric(v), value)):
+ return list(map(lambda v: float(v), value))
+ raise TypeError("Could not convert %s to list of floats" % value)
+
+ @staticmethod
+ def toListInt(value):
+ """
+ Convert a value to list of ints, if possible.
+ """
+ if TypeConverters._can_convert_to_list(value):
+ value = TypeConverters.toList(value)
+ if all(map(lambda v: TypeConverters._is_integer(v), value)):
+ return list(map(lambda v: int(v), value))
+ raise TypeError("Could not convert %s to list of ints" % value)
+
+ @staticmethod
+ def toListString(value):
+ """
+ Convert a value to list of strings, if possible.
+ """
+ if TypeConverters._can_convert_to_list(value):
+ value = TypeConverters.toList(value)
+ if all(map(lambda v: TypeConverters._is_string(v), value)):
+ return list(map(lambda v: str(v), value))
+ raise TypeError("Could not convert %s to list of strings" % value)
+
+ @staticmethod
+ def toVector(value):
+ """
+ Convert a value to a MLlib Vector, if possible.
+ """
+ if isinstance(value, Vector):
+ return value
+ elif TypeConverters._can_convert_to_list(value):
+ value = TypeConverters.toList(value)
+ if all(map(lambda v: TypeConverters._is_numeric(v), value)):
+ return DenseVector(value)
+ raise TypeError("Could not convert %s to vector" % value)
+
+ @staticmethod
+ def toFloat(value):
+ """
+ Convert a value to a float, if possible.
+ """
+ if TypeConverters._is_numeric(value):
+ return float(value)
+ else:
+ raise TypeError("Could not convert %s to float" % value)
+
+ @staticmethod
+ def toInt(value):
+ """
+ Convert a value to an int, if possible.
+ """
+ if TypeConverters._is_integer(value):
+ return int(value)
+ else:
+ raise TypeError("Could not convert %s to int" % value)
+
+ @staticmethod
+ def toString(value):
+ """
+ Convert a value to a string, if possible.
+ """
+ if TypeConverters._is_string(value):
+ return str(value)
+ else:
+ raise TypeError("Could not convert %s to string" % value)
+
+ @staticmethod
+ def toBoolean(value):
+ """
+ Convert a value to a boolean, if possible.
+ """
+ if type(value) == bool:
+ return value
+ else:
+ raise TypeError("Could not convert %s to bool" % value)
--- End diff --
Since this is a bit strict, maybe we should say in the error: "Boolean
Param requires value of type bool. Found type %s"
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