Merge pull request #86 from johentsch/44-incipits

Allow metronome mark to appear in MC 2

src/ms3/bs4_parser.py

@@ -471,8 +471,12 @@ def perform_checks(self):
         by extension, by ms3 review, too)."""
         # check if the first measure includes a metronome mark
         events = self._events
-        first_bar_event_types = events.loc[events.mc == 1, "event"]
-        if 'Tempo' not in first_bar_event_types.values:
+        first_two_mcs_event_types = events.loc[events.mc.isin((1,2)), "event"]
+        metronome_mark_missing = True
+        if 'Tempo' in first_two_mcs_event_types.values:
+            metronome_mark_missing = False
+        # here we could insert logic for treating incipit measure groups differently
+        if metronome_mark_missing:
             msg = "No metronome mark found in the very first measure"
             tempo_selector = (events.event == 'Tempo').fillna(False)
             if tempo_selector.sum() == 0:

src/ms3/transformations.py

@@ -47,12 +47,12 @@ def add_quarterbeats_col(df: pd.DataFrame,
                          offset_dict: Union[pd.Series, dict],
                          interval_index: bool = False) -> pd.DataFrame:
     """ Insert a column measuring the distance of events from MC 1 in quarter notes. If no 'mc_onset' column is present,
-        the column corresponds to the values given in the offset_dict..
+        the column corresponds to the values given in the offset_dict.
 
     Parameters
     ----------
     df : :obj:`pandas.DataFrame`
-        DataFrame with an ``mc_playthrough`` and an ``mc_onset`` column.
+        DataFrame with an ``mc`` or ``mc_playthrough`` column, and an ``mc_onset`` column.
     offset_dict : :obj:`pandas.Series` or :obj:`dict`, optional
         | If unfolded: {mc_playthrough -> offset}
         | Otherwise: {mc -> offset}