feat: add ChoiceListParameter

luigi/__init__.py

@@ -40,9 +40,9 @@
     DateIntervalParameter, TimeDeltaParameter,
     IntParameter, FloatParameter, BoolParameter, PathParameter,
     TaskParameter, EnumParameter, DictParameter, ListParameter, TupleParameter, EnumListParameter,
-    NumericalParameter, ChoiceParameter, OptionalParameter, OptionalStrParameter,
-    OptionalIntParameter, OptionalFloatParameter, OptionalBoolParameter, OptionalPathParameter,
-    OptionalDictParameter, OptionalListParameter, OptionalTupleParameter,
+    NumericalParameter, ChoiceParameter, ChoiceListParameter, OptionalParameter,
+    OptionalStrParameter, OptionalIntParameter, OptionalFloatParameter, OptionalBoolParameter,
+    OptionalPathParameter, OptionalDictParameter, OptionalListParameter, OptionalTupleParameter,
     OptionalChoiceParameter, OptionalNumericalParameter,
 )
 
@@ -66,9 +66,9 @@
     'FloatParameter', 'BoolParameter', 'PathParameter', 'TaskParameter',
     'ListParameter', 'TupleParameter', 'EnumParameter', 'DictParameter', 'EnumListParameter',
     'configuration', 'interface', 'local_target', 'run', 'build', 'event', 'Event',
-    'NumericalParameter', 'ChoiceParameter', 'OptionalParameter', 'OptionalStrParameter',
-    'OptionalIntParameter', 'OptionalFloatParameter', 'OptionalBoolParameter', 'OptionalPathParameter',
-    'OptionalDictParameter', 'OptionalListParameter', 'OptionalTupleParameter',
+    'NumericalParameter', 'ChoiceParameter', 'ChoiceListParameter', 'OptionalParameter',
+    'OptionalStrParameter', 'OptionalIntParameter', 'OptionalFloatParameter', 'OptionalBoolParameter',
+    'OptionalPathParameter', 'OptionalDictParameter', 'OptionalListParameter', 'OptionalTupleParameter',
     'OptionalChoiceParameter', 'OptionalNumericalParameter', 'LuigiStatusCode',
     '__version__',
 ]

luigi/parameter.py

@@ -1540,6 +1540,53 @@ def normalize(self, var):
                 var=var, choices=self._choices))
 
 
+class ChoiceListParameter(ChoiceParameter):
+    """
+    A parameter which takes two values:
+        1. an instance of :class:`~collections.Iterable` and
+        2. the class of the variables to convert to.
+
+    Values are taken to be a list, i.e. order is preserved, duplicates may occur, and empty list is possible.
+
+    In the task definition, use
+
+    .. code-block:: python
+
+        class MyTask(luigi.Task):
+            my_param = luigi.ChoiceListParameter(choices=['foo', 'bar', 'baz'], var_type=str)
+
+    At the command line, use
+
+    .. code-block:: console
+
+        $ luigi --module my_tasks MyTask --my-param foo,bar
+
+    Consider using :class:`~luigi.EnumListParameter` for a typed, structured
+    alternative.  This class can perform the same role when all choices are the
+    same type and transparency of parameter value on the command line is
+    desired.
+    """
+
+    _sep = ','
+
+    def __init__(self, *args, **kwargs):
+        super(ChoiceListParameter, self).__init__(*args, **kwargs)
+
+    def parse(self, s):
+        values = [] if s == '' else s.split(self._sep)
+        return self.normalize(map(self._var_type, values))
+
+    def normalize(self, var):
+        values = []
+        for v in var:
+            values.append(super().normalize(v))
+        return tuple(values)
+
+
+    def serialize(self, values):
+        return self._sep.join(values)
+
+
 class OptionalChoiceParameter(OptionalParameterMixin, ChoiceParameter):
     """Class to parse optional choice parameters."""
 

test/parameter_test.py

@@ -310,6 +310,25 @@ def test_enum_list_param_invalid(self):
     def test_enum_list_param_missing(self):
         self.assertRaises(ParameterException, lambda: luigi.parameter.EnumListParameter())
 
+    def test_choice_list_param_valid(self):
+        p = luigi.parameter.ChoiceListParameter(choices=["1", "2", "3"])
+        self.assertEqual((), p.parse(''))
+        self.assertEqual(("1",), p.parse('1'))
+        self.assertEqual(("1", "3"), p.parse('1,3'))
+
+    def test_choice_list_param_invalid(self):
+        p = luigi.parameter.ChoiceListParameter(choices=["1", "2", "3"])
+        self.assertRaises(ValueError, lambda: p.parse('1,4'))
+
+    def test_invalid_choice_type(self):
+        self.assertRaises(
+            AssertionError,
+            lambda: luigi.ChoiceListParameter(var_type=int, choices=[1, 2, "3"]),
+        )
+
+    def test_choice_list_param_missing(self):
+        self.assertRaises(ParameterException, lambda: luigi.parameter.ChoiceListParameter())
+
     def test_tuple_serialize_parse(self):
         a = luigi.TupleParameter()
         b_tuple = ((1, 2), (3, 4))
@@ -469,6 +488,13 @@ class FooWithDefault(luigi.Task):
 
         self.assertEqual(FooWithDefault().args, p.parse('C'))
 
+    def test_choice_list(self):
+        class Foo(luigi.Task):
+            args = luigi.ChoiceListParameter(var_type=str, choices=["1", "2", "3"])
+
+        p = luigi.ChoiceListParameter(var_type=str, choices=["3", "2", "1"])
+        self.assertEqual(hash(Foo(args=("3",)).args), hash(p.parse("3")))
+
     def test_dict(self):
         class Foo(luigi.Task):
             args = luigi.parameter.DictParameter()