Use hasattr() rather than isinstance(value, MutableSequence)

booby/encoders.py

@@ -37,7 +37,7 @@ def __init__(self, *encoders):
 
     @nullable
     def encode(self, value):
-        if not isinstance(value, collections.MutableSequence):
+        if not hasattr(value, '__iter__'):
             raise errors.EncodeError()
 
         result = []

booby/fields.py

@@ -245,7 +245,7 @@ def __init__(self, model, *args, **kwargs):
         self.model = model
 
     def __set__(self, instance, value):
-        if isinstance(value, collections.MutableSequence):
+        if hasattr(value, '__iter__'):
             value = self._resolve(value)
 
         super(Collection, self).__set__(instance, value)

booby/models.py

@@ -110,14 +110,19 @@ def __iter__(self):
 
             if isinstance(value, Model):
                 value = dict(value)
-            elif isinstance(value, collections.MutableSequence):
-                value = self._encode_sequence(value)
+            if hasattr(value, '__iter__'):
+                value = self._encode_iterable(value)
 
             yield name, value
 
-    def _encode_sequence(self, sequence):
+    def _encode_iterable(self, sequence):
         result = []
 
+        if isinstance(sequence, (dict, basestring)):
+            # Although iterable, dictionaries are a special
+            # case and should be used as-is
+            return sequence
+
         for value in sequence:
             if isinstance(value, Model):
                 value = dict(value)

booby/validators.py

@@ -157,7 +157,9 @@ def __init__(self, *validators):
 
     @nullable
     def validate(self, value):
-        if not isinstance(value, collections.MutableSequence):
+        # Note: Strings are iterable in python3, but we are not going
+        # to count strings as valid lists here.
+        if not hasattr(value, '__iter__') or isinstance(value, basestring):
             raise errors.ValidationError('should be a list')
 
         for i in value:

tests/unit/models/test_model.py

@@ -177,7 +177,6 @@ class UserWithToken(User):
 
         user = dict(UserWithToken(name='foo', email='[email protected]',
                                   token=self.token1))
-
         expect(user).to(have_keys(
             name='foo',
             email='[email protected]',