ADD helper methods to get/create RandomState - work on #2

hpolib/util/rng_helper.py

@@ -0,0 +1,36 @@
+import numpy as np
+
+
+def get_rng(rng=None, self_rng=None):
+    """ helper function to obtain RandomState.
+    returns RandomState created from rng
+    if rng is None returns self_rng if RandomState
+    if self_rng is None initializes RandomState at random
+
+    :param rng: int or RandomState
+    :param self_rng: RandomState
+    :return: RandomState
+    """
+
+    if rng is not None:
+        return create_rng(rng)
+    elif rng is None and self_rng is not None:
+        return create_rng(self_rng)
+    else:
+        return np.random.RandomState()
+
+
+def create_rng(rng):
+    """ helper to create rng from RandomState or int
+    :param rng: int or RandomState
+    :return: RandomState
+    """
+    if rng is None:
+        return np.random.RandomState()
+    elif type(rng) == np.random.RandomState:
+        return rng
+    elif int(rng) == rng:
+        return np.random.RandomState(rng)
+    else:
+        raise ValueError("%s is neither a number nor a RandomState. "
+                         "Initializing RandomState failed")