allow specifying budget class to load

By default the budget class loaded will have the same name as the budget
module.  This adds the ability to specify which budget class to load,
allowing for loading sub-budgets directly.

Hooks added to the CLI as well.

gwinc/__init__.py

@@ -74,20 +74,25 @@ def load_module(name_or_path):
     return mod, path
 
 
-def load_budget(name_or_path, freq=None):
+def load_budget(name_or_path, freq=None, bname=None):
     """Load GWINC Budget
 
     Accepts either the name of a built-in canonical budget (see
     gwinc.IFOS), the path to a budget package (directory) or module
     (ending in .py), or the path to an IFO Struct definition file (see
-    gwinc.Struct).
+    gwinc.Struct).  If an IFO Struct is specified, the base "aLIGO"
+    budget definition will be used.
+
+    If `bname` is specified the Budget class with that name will be
+    loaded from the budget module.  Otherwise, the Budget class with
+    the same name as the budget module will be load.
 
     If the budget is a package directory which includes an 'ifo.yaml'
     file the ifo Struct will be loaded from that file and assigned to
     the budget.ifo attribute.  If a Struct definition file is provided
     the base aLIGO budget definition will be assumed.
 
-    Returns an instantiated Budget object.  If a frequency array or
+    Returns the instantiated Budget object.  If a frequency array or
     frequency specification string (see `freq_from_spec()`) is
     provided, the budget will be instantiated with the provided array.
     If a frequency array is not provided and the Budget class
@@ -103,7 +108,7 @@ def load_budget(name_or_path, freq=None):
 
     if os.path.exists(name_or_path):
         path = name_or_path.rstrip('/')
-        bname, ext = os.path.splitext(os.path.basename(path))
+        base, ext = os.path.splitext(os.path.basename(path))
 
         if ext in Struct.STRUCT_EXT:
             logger.info("loading struct {}...".format(path))
@@ -112,6 +117,7 @@ def load_budget(name_or_path, freq=None):
             modname = 'gwinc.ifo.aLIGO'
 
         else:
+            bname = bname or base
             modname = path
 
     else:
@@ -120,10 +126,10 @@ def load_budget(name_or_path, freq=None):
                 name_or_path,
                 IFOS,
             ))
-        bname = name_or_path
+        bname = bname or name_or_path
         modname = 'gwinc.ifo.'+name_or_path
 
-    logger.info("loading module {}...".format(modname))
+    logger.info(f"loading budget {modname}.{bname}...")
     mod, modpath = load_module(modname)
     Budget = getattr(mod, bname)
     if freq is None:

gwinc/__main__.py

@@ -105,6 +105,9 @@ group.add_argument(
 parser.add_argument(
     '--no-plot', '-np', action='store_false', dest='plot',
     help="suppress plotting")
+parser.add_argument(
+    '--bname', '-b',
+    help="name of top-level Budget class to load (defaults to IFO name)")
 parser.add_argument(
     'IFO',
     help="IFO name or path")
@@ -137,7 +140,7 @@ def main():
         except IndexError:
             parser.error(f"Improper frequency specification: {args.freq}")
         try:
-            budget = load_budget(args.IFO, freq=freq)
+            budget = load_budget(args.IFO, freq=freq, bname=args.bname)
         except RuntimeError as e:
             parser.exit(2, f"Error: {e}\n")
         name = budget.name