finish US-SEC: merge gas/coal from EIA with solar

for electricitymaps#1713

uses `ENTSOE.merge_production_outputs()`, and there isn't much precedent for parsers reusing, so i've also added a TODO to move that function to `lib.utils`.

parsers/ENTSOE.py

@@ -857,6 +857,8 @@ def fetch_production(zone_key, session=None, target_datetime=None,
 }
 
 
+# TODO: generalize and move to lib.utils so other parsers can reuse it. (it's
+# currently used by US_SEC.)
 def merge_production_outputs(parser_outputs, merge_zone_key, merge_source=None):
     """
     Given multiple parser outputs, sum the production and storage

parsers/US_SEC.py

@@ -2,6 +2,8 @@
 
 """Parser for the Seminole Electric Cooperative in Florida, USA.
 
+https://www.seminole-electric.com/facilities/generation/
+http://apps.seminole.coop/db/cs/
 https://github.com/tmrowco/electricitymap-contrib/issues/1713
 """
 
@@ -10,41 +12,51 @@
 
 import pandas as pd
 
-import EIA
+from parsers import EIA
+from parsers.ENTSOE import merge_production_outputs
 
 
-def fetch_production(zone_key='US-SEC', session=None,
-                     target_datetime=None, logger=logging.getLogger(__name__)):
-    """Requests the last known production mix (in MW) of a given country
+def fetch_production(zone_key='US-SEC', session=None, target_datetime=None,
+                     logger=logging.getLogger(__name__)):
+    unknown = fetch_unknown(zone_key=zone_key, session=session,
+                            target_datetime=target_datetime, logger=logger)
+    solar = fetch_solar(session=session, logger=logger)
+    return merge_production_outputs((unknown, solar), zone_key,
+                                    merge_source='eia.org, apps.seminole.coop')
 
-    See example.py for details.
-    """
+
+def fetch_unknown(zone_key='US-SEC', session=None, target_datetime=None,
+                  logger=logging.getLogger(__name__)):
     data = EIA.fetch_production(zone_key=zone_key, session=session,
                                 target_datetime=target_datetime, logger=logger)
     for hour in data:
-        hour['production'] = {'unknown': hour.pop('value')}
+        hour.update({
+            'production': {'unknown': hour.pop('value')},
+            'storage': {},  # required by merge_production_outputs
+        })
 
     return data
 
 
 def fetch_solar(session=None, logger=logging.getLogger(__name__)):
-    url = 'http://apps.seminole.coop/db/cs/render.ashx?ItemPath=/Applications/Solar+Dashboard/Cooperative+Solar+-+Data&Format=EXCEL&rptHDInterval=Day&rptHDOffset=0'
+    url = 'http://apps.seminole.coop/db/cs/render.ashx?ItemPath=/Applications/Solar+Dashboard/Cooperative+Solar+-+Data&Format=EXCEL&rptHDInterval=Week&rptHDOffset=0'
     df = pd.read_excel(url, sheet_name='Hourly', skiprows=[0])
 
     return [{
-        'zoneKey': 'US_SEC',
+        'zoneKey': 'US-SEC',
         'datetime': row['Date/Time (UTC)'].to_pydatetime().replace(tzinfo=timezone.utc),
         'production': {'solar': row['kW'] / 1000.0},
+        'storage': {},  # required by merge_production_outputs
         'source': 'apps.seminole.coop',
     } for _, row in df.iterrows()]
 
 
-
-if __name__ == '__main__':
+def main():
     """Main method, not used by the ElectricityMap backend, just for testing."""
-
     import pprint
     print('fetch_production() ->')
-    print(pprint.pprint(fetch_production(target_datetime='20190705T22Z')))
-    print('fetch_solar() ->')
-    print(pprint.pprint(fetch_solar()))
+    print(pprint.pprint(fetch_production()))
+
+
+if __name__ == '__main__':
+    main()