Contains validation for the scheme validator

voluptuous/error.py

@@ -101,6 +101,10 @@ class ValueInvalid(Invalid):
     """The value was found invalid by evaluation function."""
 
 
+class ContainsInvalid(Invalid):
+    """List does not contain item"""
+
+
 class ScalarInvalid(Invalid):
     """Scalars did not match."""
 

voluptuous/tests/tests.py

@@ -6,7 +6,8 @@
     Schema, Required, Optional, Extra, Invalid, In, Remove, Literal,
     Url, MultipleInvalid, LiteralInvalid, NotIn, Match, Email,
     Replace, Range, Coerce, All, Any, Length, FqdnUrl, ALLOW_EXTRA, PREVENT_EXTRA,
-    validate, ExactSequence, Equal, Unordered, Number, Maybe, Datetime, Date
+    validate, ExactSequence, Equal, Unordered, Number, Maybe, Datetime, Date,
+    Contains
 )
 from voluptuous.humanize import humanize_error
 from voluptuous.util import to_utf8_py2, u
@@ -73,6 +74,17 @@ def test_not_in():
         assert False, "Did not raise NotInInvalid"
 
 
+def test_contains():
+    """Verify contains validation method."""
+    schema = Schema({'color': Contains('red')})
+    schema({'color': ['blue', 'red', 'yellow']})
+    try:
+        schema({'color': ['blue', 'yellow']})
+    except Invalid as e:
+        assert_equal(str(e),
+                    "value is not allowed for dictionary value @ data['color']")
+
+
 def test_remove():
     """Verify that Remove works."""
     # remove dict keys

voluptuous/validators.py

@@ -10,13 +10,13 @@
     from error import (MultipleInvalid, CoerceInvalid, TrueInvalid, FalseInvalid, BooleanInvalid, Invalid, AnyInvalid,
                        AllInvalid, MatchInvalid, UrlInvalid, EmailInvalid, FileInvalid, DirInvalid, RangeInvalid,
                        PathInvalid, ExactSequenceInvalid, LengthInvalid, DatetimeInvalid, DateInvalid, InInvalid,
-                       TypeInvalid, NotInInvalid)
+                       TypeInvalid, NotInInvalid, ContainsInvalid)
 except ImportError:
     from .schema_builder import Schema, raises, message
     from .error import (MultipleInvalid, CoerceInvalid, TrueInvalid, FalseInvalid, BooleanInvalid, Invalid, AnyInvalid,
                         AllInvalid, MatchInvalid, UrlInvalid, EmailInvalid, FileInvalid, DirInvalid, RangeInvalid,
                         PathInvalid, ExactSequenceInvalid, LengthInvalid, DatetimeInvalid, DateInvalid, InInvalid,
-                        TypeInvalid, NotInInvalid)
+                        TypeInvalid, NotInInvalid, ContainsInvalid)
 
 
 if sys.version_info >= (3,):
@@ -680,6 +680,26 @@ def __repr__(self):
         return 'NotIn(%s)' % (self.container,)
 
 
+class Contains(object):
+    """Validate that a value is in a collection."""
+
+    def __init__(self, item, msg=None):
+        self.item = item
+        self.msg = msg
+
+    def __call__(self, v):
+        try:
+            check = self.item not in v
+        except TypeError:
+            check = True
+        if check:
+            raise ContainsInvalid(self.msg or 'value is not allowed')
+        return v
+
+    def __repr__(self):
+        return 'Contains(%s)' % (self.item, )
+
+
 class ExactSequence(object):
     """Matches each element in a sequence against the corresponding element in
     the validators.