Create ResultsList instead of trying to add an __add__ method

bilby/core/result.py

@@ -1188,31 +1188,127 @@ class Result(object):
                                  "keyword argument, e.g. " + caller_func.__name__ + "(outdir='.')")
         return outdir
 
-    def __add__(self, other):
+
+class ResultsList(object):
+
+    def __init__(self, results=None):
+        """ A class to store a list of :class:`bilby.core.result.Result` objects
+        from equivalent runs on the same data. This provides methods for
+        outputing combined results.
+
+        Parameters
+        ----------
+        results: list
+            A :class:`bilby.core.result.Result` object, or list of
+            results.
+        """
+
+        self.results = results
+        self.__currentidx = 0  # index for iterator
+
+    @property
+    def results(self):
+        return self._results
+
+    @results.setter
+    def results(self, results):
+        self._results = []  # empty list
+        if results is None:
+            return
+
+        self.append(results)
+
+    def append(self, results):
+        """
+        Append a :class:`bilby.core.result.Result`, or set of results, to the
+        list.
+
+        Parameters
+        ----------
+        results: :class:`bilby.core.result.Result`, or list of results
+            A :class:`bilby.core.result.Result`, list of
+            :class:`bilby.core.result.Result` object, or list of filenames
+            pointing to results objects, to append to the list.
+        """
+
+        if not isinstance(results, (list, ResultsList)):
+            results = [results]  # make into list for iteration
+
+        # loop over list
+        for result in results:
+            if isinstance(result, Result):
+                # append new result
+                self._results.append(result)
+            elif isinstance(result, str):
+                # try reading from file
+                try:
+                    self._results.append(read_in_result(result))
+                except Exception as e:
+                    raise IOError("Could not read in results file: "
+                                  "{}".format(e))
+            else:
+                raise TypeError("Could not append a non-Result type")
+
+    def __len__(self):
+        return len(self.results)
+
+    def __iter__(self):
+        self.__currentidx = 0  # reset iterator index
+        return self
+
+    def __next__(self):
+        if self.__currentidx >= len(self):
+            raise StopIteration
+        else:
+            self.__currentidx += 1
+            return self.results[self.__currentidx - 1]
+
+    next = __next__  # Python 2 next
+
+    def combine(self):
         """
-        Method to add two Results objects.
+        Return the combined results in a :class:bilby.core.result.Result`
+        object.
         """
 
-        if not isinstance(other, Result):
-            raise TypeError("Trying to add a non-Result object to a Result "
-                            "object")
+        from copy import deepcopy
+
+        if len(self) == 0:
+            return Result()
+        elif len(self) == 1:
+            return deepcopy(self.results[0])
+        else:
+            # get first result
+            result = deepcopy(self.results[0])
+
+        # check all results are equivalent
+        sampler = result.sampler
+        if not np.all([res.sampler == sampler for res in self]):
+            raise ValueError("Cannot combine results: inconsistent samplers")
+
+        log_noise_evidence = result.log_noise_evidence
+        if not np.all([res.log_noise_evidence == log_noise_evidence for res in self]):
+            raise ValueError("Cannot combine results: inconsistent data")
 
-        # check that the results have some common features
+        parameters = result.search_parameter_keys
+        if not np.all([set(parameters) == set(res.search_parameter_keys) for res in self]):
+            raise ValueError("Cannot combine results: inconsistent parameters")
 
-        # check parameters are the same
-        if not set(self.search_parameter_keys) == set(other.search_parameter_keys):
-            raise ValueError("Results being added contain inconsistent parameters")
+        priors = result.priors
+        for result in self:
+            for p in parameters:
+                if not priors[p] == result.priors[p]:
+                    raise ValueError("Cannot combine results: inconsistent priors")
 
-        if self.log_noise_evidence != other.log_noise_evidence:
-            raise ValueError("Results being added do not have consistent "
-                             "noise evidences")
+        # check which kind of sampler was used: MCMC or Nested Sampling
+        if result.nested_samples is not None:
+            if not np.all([res.nested_samples is not None for res in self]):
+                raise ValueError("Cannot combine results: nested samples available")
 
-        # check priors are the same
-        if self.priors is not None and other.priors is not None:
-            for p in self.search_parameter_keys:
-                if not self.priors[p] == other.priors[p]:
-                    raise ValueError("Results being added used inconsistent "
-                                     "priors") 
+            # combine all nested samples
+
+        else:
+            # combine MCMC samples
 
 
 def plot_multiple(results, filename=None, labels=None, colours=None,