[Enhancement Proposal]: different types for 'nargs' > 1

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Right now an Option with 'nargs' > 1 accept n arguments of the same all 
of the same 'type'.

What I'd find usefull is the possibility to set the type of each 
argument indipendently, ie. something like
	type = ('choice', 'float')
wich is automatically transformed in
	type = 'tuple',
	types = ('choice', 'float')
BTW, these should automatically instruct Option to consume 2 arguments 
(nargs = 2).

So far, I've implemented all this, introducing these changes to Option:
  - new type (and type checker): 'tuple' (and check_tuple)
  - new class attribute/constructor keyword: 'types', to hold the tuple
      of types
  - modified _check_type to check 'tuple' as a type and then each type
    inside the tuple
  - modified some type check from
	something == 'type'
    to
	something == 'type' or ('tuple' == self.type and something in self.types)
and some minor ones here and there, to hold it all together.

I've implemented this either as a subclass or as a patch agains 
option.py (CVS 1.51a). The latter is attached.

Hope anyone finds this interesting and/or usefull :-)

.fw.

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? build
Index: lib/option.py
===================================================================
RCS file: /cvsroot/optik/optik/lib/option.py,v
retrieving revision 1.33
diff -u -3 -p -r1.33 option.py
--- lib/option.py	24 Jul 2004 23:21:21 -0000	1.33
+++ lib/option.py	20 Oct 2004 17:08:45 -0000
@@ -43,6 +43,11 @@ def check_choice(option, opt, value):
             _("option %s: invalid choice: %r (choose from %s)")
             % (opt, value, choices))
 
+def check_tuple(option, opt, value):
+    value = [option.check_value(opt, v) for (v, option.type) in map(None, value, option.types)]
+    option.type = "tuple"
+    return tuple(value)
+
 # Not supplying a default is different from a default of None,
 # so we need an explicit "not supplied" value.
 NO_DEFAULT = ("NO", "DEFAULT")
@@ -55,7 +60,8 @@ class Option:
       _long_opts : [string]
 
       action : string
-      type : string
+      type : { string | tuple of strings | list of strings }
+      types : { tuple of strings | list of strings } 
       dest : string
       default : any
       nargs : int
@@ -72,6 +78,7 @@ class Option:
     # keyword args to the constructor.
     ATTRS = ['action',
              'type',
+             'types',
              'dest',
              'default',
              'nargs',
@@ -113,7 +120,7 @@ class Option:
 
     # The set of known types for option parsers.  Again, listed here for
     # constructor argument validation.
-    TYPES = ("string", "int", "long", "float", "complex", "choice")
+    TYPES = ("string", "int", "long", "float", "complex", "choice", "tuple")
 
     # Dictionary of argument checking functions, which convert and
     # validate option arguments according to the option type.
@@ -136,6 +143,7 @@ class Option:
                      "float"  : check_builtin,
                      "complex": check_builtin,
                      "choice" : check_choice,
+                     "tuple"  : check_tuple,
                    }
 
 
@@ -226,6 +234,22 @@ class Option:
             raise OptionError("invalid action: %r" % self.action, self)
 
     def _check_type(self):
+        if type(self.type) in (types.TupleType, types.ListType):
+            if not self.type:
+                # take care of empty sequences
+                self.type = None
+            else:
+                # check each type, and save them in 'types'
+                self.types = tuple([self._check_type() for self.type in self.type])
+                self.type = "tuple"
+        elif self.type == "tuple":
+            if type(self.types) not in (types.TupleType, types.ListType):
+                raise OptionError("must supply a list or tuple of types for type 'tuple'", self)
+            else:
+                # check each type, and save them in 'types'
+                self.types = tuple([self._check_type() for self.type in self.types])
+                self.type = "tuple"
+
         if self.type is None:
             # XXX should factor out another class attr here: list of
             # actions that *require* a type
@@ -248,9 +272,11 @@ class Option:
             if self.action not in self.TYPED_ACTIONS:
                 raise OptionError(
                     "must not supply a type for action %r" % self.action, self)
+        # return the final type - usefull for checking "tuple" types
+        return self.type
 
     def _check_choice(self):
-        if self.type == "choice":
+        if self.type == "choice" or (self.type == "tuple" and "choice" in self.types):
             if self.choices is None:
                 raise OptionError(
                     "must supply a list of choices for type 'choice'", self)
@@ -286,7 +312,12 @@ class Option:
     def _check_nargs(self):
         if self.action in self.TYPED_ACTIONS:
             if self.nargs is None:
-                self.nargs = 1
+                if self.type == "tuple":
+                    self.nargs = len(self.types)
+                else:
+                    self.nargs = 1
+            elif self.type == "tuple" and self.nargs != len(self.types):
+                raise OptionError("if supplied, 'nargs' must be equal to len('types')", self)
         elif self.nargs is not None:
             raise OptionError(
                 "'nargs' must not be supplied for action %r" % self.action,
@@ -358,7 +389,7 @@ class Option:
 
     def convert_value(self, opt, value):
         if value is not None:
-            if self.nargs == 1:
+            if self.nargs == 1 or self.type == "tuple":
                 return self.check_value(opt, value)
             else:
                 return tuple([self.check_value(opt, v) for v in value])

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