Bug/Require OrderedDict for Scans input (#99)

* check that a multiscan input is an ordered dictionary
* updated test to check for `dict` type checking error

neutronpy/data/scans.py

@@ -5,14 +5,15 @@
 import matplotlib.pyplot as plt
 import matplotlib.colors as mpl_c
 import numpy as np
+import collections
 
 
 class Scans(object):
     r"""A class for a collection of scans
 
     Attributes
     ----------
-    scans : dict
+    scans : Ordered dict
         A dictionary of scan objects
     num_scans : int
         The number of scans
@@ -25,9 +26,11 @@ class Scans(object):
     """
 
     def __init__(self, scans_dict=None):
-        self.scans = scans_dict
         if scans_dict is not None:
+            if not isinstance(scans_dict,collections.OrderedDict):
+                raise RuntimeError("the input dictionary must be of type OrderedDict")
             self.num_scans = len(scans_dict)
+        self.scans = scans_dict
 
     def update(self, scans_dict):
         r"""Update the scans_dict to include the dictionary scans_dict
@@ -40,6 +43,8 @@ def update(self, scans_dict):
               A dictionary of multiple scans to add to the collection.
 
         """
+        if not isinstance(scans_dict,collections.OrderedDict):
+            raise RuntimeError("the input dictionary must be of type OrderedDict")
         self.scans.update(scans_dict)
         self.num_scans = len(scans_dict)
 

tests/test_scans.py

@@ -7,6 +7,7 @@
 import neutronpy.fileio as npyio
 import os
 import pytest
+import collections
 from mock import patch
 
 
@@ -16,7 +17,7 @@ def load_scans(start,stop):
     """
     Creates a dictionary of scans for use in other test functions
     """
-    scansin={}
+    scansin=collections.OrderedDict()
     try:
       for idx in range(start,stop+1):
          scansin[idx]=npyio.load_data(os.path.join(os.path.dirname(__file__),'filetypes/HB1A/HB1A_exp0718_scan0%d.dat'%idx))
@@ -26,12 +27,23 @@ def load_scans(start,stop):
 
 
 def test_scans_init():
+  #load file
   scansin=load_scans(222,243)
-
+  # check expecteed execution
   try:
-      npysc.Scans(scans_dict=scansin)
+      tst_obj=npysc.Scans(scans_dict=scansin)
   except:
       pytest.failed('could not build scan collection')
+  # check if appropriate error is raise if not an ordered dict.
+  dict_scans=dict(scansin)
+  with pytest.raises(RuntimeError) as excinfo:
+      npysc.Scans(scans_dict=dict_scans)
+  assert 'type OrderedDict' in str(excinfo.value)
+  # check that update raises the proper error
+  with pytest.raises(RuntimeError) as excinfo:
+      tst_obj.update(dict_scans)
+  assert 'type OrderedDict' in str(excinfo.value)
+
 
 @patch('matplotlib.pyplot.show')
 def test_pcolor(mock_show):