making sure that if last_no_of_packets is not specified that it is se…

…t to no_of_packets + test

tardis/data/tardis_config_definition.yml

@@ -288,9 +288,11 @@ montecarlo:
 
     last_no_of_packets:
         property_type: int
-        default: 100
+        default: -1
         mandatory: False
-        help: This can set the number of packets for the last run. If set to None it will remain the same as all other runs.
+        help: >
+            This can set the number of packets for the last run.
+            If set negative it will remain the same as all other runs.
 
     no_of_virtual_packets:
         property_type: int

tardis/io/config_reader.py

@@ -1012,6 +1012,9 @@ def from_config_dict(cls, config_dict, atom_data=None, test_parser=False,
         ##### Monte Carlo Section
 
         montecarlo_section = validated_config_dict['montecarlo']
+        if montecarlo_section['last_no_of_packets'] < 0:
+            montecarlo_section['last_no_of_packets'] = \
+                montecarlo_section['no_of_packets']
 
         default_convergence_section = {'type': 'damped',
                                       'lock_t_inner_cyles': 1,

tardis/io/tests/test_config_reader.py

@@ -126,6 +126,15 @@ def test_time_explosion(self):
         assert_almost_equal(self.config['supernova']['time_explosion'],
                             13.0 * u.day)
 
+
+def test_last_no_of_packets():
+    yaml_data = yaml.load(open(data_path('paper1_tardis_configv1.yml')))
+    del yaml_data['montecarlo']['last_no_of_packets']
+    config = config_reader.Configuration.from_config_dict(yaml_data,
+                                                          test_parser=True)
+    assert (config.montecarlo.last_no_of_packets ==
+            config.montecarlo.no_of_packets)
+
 class TestParseConfigV1ASCIIDensity:
 
     def setup(self):