Allows users to give priors as an OrderedDict

By putting in the dictionary as an ordered dict, the way priors are entered determines the order they are plotted, which is what most people will expect.

• Also adds some catches to help improve error messages for when the input prior is something else.

tupak/core/prior.py

@@ -7,12 +7,13 @@ from scipy.integrate import cumtrapz
 from scipy.special import erf, erfinv
 import scipy.stats
 import os
+from collections import OrderedDict
 
 from tupak.core.utils import logger
 from tupak.core import utils
 
 
-class PriorSet(dict):
+class PriorSet(OrderedDict):
     def __init__(self, dictionary=None, filename=None):
         """ A set of priors
 
@@ -23,8 +24,8 @@ class PriorSet(dict):
         filename: str, None
             If given, a file containing the prior to generate the prior set.
         """
-        dict.__init__(self)
-        if type(dictionary) is dict:
+        OrderedDict.__init__(self)
+        if type(dictionary) in [dict, OrderedDict]:
             self.update(dictionary)
         elif type(dictionary) is str:
             logger.debug('Argument "dictionary" is a string.'
@@ -32,6 +33,8 @@ class PriorSet(dict):
             self.read_in_file(dictionary)
         elif type(filename) is str:
             self.read_in_file(filename)
+        elif dictionary is not None:
+            raise ValueError("PriorSet input dictionay not understood")
 
     def write_to_file(self, outdir, label):
         """ Write the prior distribution to file.