Added dict_combine function for Python 2 compatibility

sciunit/tests.py

@@ -12,6 +12,7 @@
 from .validators import ObservationValidator, ParametersValidator
 from .errors import Error, CapabilityError, ObservationError,\
                     InvalidScoreError, ParametersError
+from .utils import dict_combine
 
 
 class Test(SciUnit):
@@ -32,7 +33,7 @@ def __init__(self, observation, name=None, **params):
 
         # Use a combination of default_params and params, choosing the latter
         # if there is a conflict.
-        self.params = {**self.default_params, **params}
+        self.params = dict_combine(self.default_params, params)
         self.verbose = self.params.pop('verbose', 1)
         self.validate_params(self.params)
         # Compute possible new params from existing params

sciunit/utils.py

@@ -67,6 +67,16 @@ def set_warnings_traceback(tb=True):
         warnings.simplefilter("default")
 
 
+def dict_combine(*dict_list): 
+    """Return the union of several dictionaries.
+    Uses the values from later dictionaries in the argument list when
+    duplicate keys are encountered.
+    In Python 3 this can simply be {**d1, **d2, ...}
+    but Python 2 does not support this dict unpacking syntax.
+    """
+    return {k: v for d in dict_list for k, v in d.items()}
+
+
 def rec_apply(func, n):
     """
     Used to determine parent directory n levels up