Clarify nargs specifiers

Rather than using raw strings, nargs specifiers are now expressed in
terms of argparse's corresponding global variables.

bonemarketsolver/__main__.py

@@ -68,7 +68,7 @@ skeleton_parameters.add_argument(
 skeleton_parameters.add_argument(
         "-b", "--buyer", "--desired-buyer",
         action=EnumAction,
-        nargs='+',
+        nargs=argparse.ONE_OR_MORE,
         type=Buyer,
         help="specific buyer that skeleton should be designed for (if multiple are specified, will choose from among them)",
         dest='desired_buyers'
@@ -91,7 +91,7 @@ skeleton_parameters.add_argument(
 skeleton_parameters.add_argument(
         "--blacklist",
         action=BlacklistAction,
-        nargs='+',
+        nargs=argparse.ONE_OR_MORE,
         help="components, options, or buyers that should not be used by the solver",
         metavar="Enum.MEMBER",
         dest='blacklist'

bonemarketsolver/objects/blacklistaction.py

@@ -1,7 +1,7 @@
 __all__ = ['BlacklistAction']
 __author__ = "Jeremy Saklad"
 
-from argparse import Action
+import argparse
 
 from ..data.adjustments import Adjustment
 from ..data.appendages import Appendage
@@ -17,7 +17,7 @@ def convert_to_enum(value):
     enum = globals()[split[0]]
     return enum[split[1]]
 
-class BlacklistAction(Action):
+class BlacklistAction(argparse.Action):
     def __init__(self, **kwargs):
         nargs = kwargs.get('nargs')
 
@@ -26,7 +26,8 @@ class BlacklistAction(Action):
         self._nargs = nargs
 
     def __call__(self, parser, namespace, values, option_string=None):
-        if self._nargs is None or self._nargs == '?':
+        # Check whether this is a single value or a list of them
+        if self._nargs is None or self._nargs == argparse.OPTIONAL:
             # Convert value back into an Enum
             enum = convert_to_enum(value)
 

bonemarketsolver/objects/enumaction.py

@@ -1,9 +1,9 @@
 __all__ = ['EnumAction']
 __author__ = "Jeremy Saklad"
 
-from argparse import Action
+import argparse
 
-class EnumAction(Action):
+class EnumAction(argparse.Action):
     def __init__(self, **kwargs):
         # Pop off the type value
         enum = kwargs.pop('type', None)
@@ -19,7 +19,8 @@ class EnumAction(Action):
         self._nargs = nargs
 
     def __call__(self, parser, namespace, values, option_string=None):
-        if self._nargs is None or self._nargs == '?':
+        # Check whether this is a single value or a list of them
+        if self._nargs is None or self._nargs == argparse.OPTIONAL:
             # Convert value back into an Enum
             enum = self._enum[values.upper()]