--- a
+++ b/sandbox/test_idx.py
@@ -0,0 +1,51 @@
+import numpy as np
+
+x = np.arange(21)
+
+part_out_of = (1, 3)
+this_part = part_out_of[0]
+all_parts = part_out_of[1]
+part_lenght = int(len(x) / all_parts)
+
+if this_part == all_parts:
+    x1 = x[part_lenght * (this_part - 1):]
+else:
+    x1 = x[part_lenght * (this_part - 1): part_lenght * this_part]
+
+print x1
+
+part_out_of = (2, 3)
+this_part = part_out_of[0]
+all_parts = part_out_of[1]
+part_lenght = int(len(x) / all_parts)
+
+if this_part == all_parts:
+    x1 = x[part_lenght * (this_part - 1):]
+else:
+    x1 = x[part_lenght * (this_part - 1): part_lenght * this_part]
+
+print x1
+
+part_out_of = (3, 3)
+this_part = part_out_of[0]
+all_parts = part_out_of[1]
+part_lenght = int(len(x) / all_parts)
+
+if this_part == all_parts:
+    x1 = x[part_lenght * (this_part - 1):]
+else:
+    x1 = x[part_lenght * (this_part - 1): part_lenght * this_part]
+
+print x1
+
+part_out_of = (4, 3)
+this_part = part_out_of[0]
+all_parts = part_out_of[1]
+part_lenght = int(len(x) / all_parts)
+
+if this_part == all_parts:
+    x1 = x[part_lenght * (this_part - 1):]
+else:
+    x1 = x[part_lenght * (this_part - 1): part_lenght * this_part]
+
+print x1