py3: introduce new kivy.compat module for checking if we are on python3, and define new "types", like string_types.

kivy/animation.py

@@ -63,6 +63,7 @@ __all__ = ('Animation', 'AnimationTransition')
 from math import sqrt, cos, sin, pi
 from kivy.event import EventDispatcher
 from kivy.clock import Clock
+from kivy.compat import string_types
 
 
 class Animation(EventDispatcher):
@@ -105,7 +106,7 @@ class Animation(EventDispatcher):
         self._duration = kw.get('d', kw.get('duration', 1.))
         self._transition = kw.get('t', kw.get('transition', 'linear'))
         self._step = kw.get('s', kw.get('step', 1. / 60.))
-        if isinstance(self._transition, str):
+        if isinstance(self._transition, string_types):
             self._transition = getattr(AnimationTransition, self._transition)
         for key in ('d', 't', 's', 'step', 'duration', 'transition'):
             kw.pop(key, None)

kivy/compat.py

@@ -0,0 +1,14 @@
+'''
+Compatibility module for Python 2.7 and > 3.3
+=============================================
+'''
+
+import sys
+
+#: True if the code is running on Python 3 interpreter.
+is_py3 = sys.version >= '3'
+
+#: String types that can be used for checking if a object is a string
+string_types = str
+if not is_py3:
+    string_types = basestring

kivy/core/image/__init__.py

@@ -21,6 +21,7 @@ from kivy.clock import Clock
 from kivy.atlas import Atlas
 from kivy.resources import resource_find
 from kivy.utils import platform
+from kivy.compat import string_types
 import zipfile
 try:
     import io as SIO
@@ -420,10 +421,10 @@ class Image(EventDispatcher):
             self._size = self.texture.size
         elif isinstance(arg, ImageLoaderBase):
             self.image = arg
-        elif isinstance(arg, str):
+        elif isinstance(arg, string_types):
             self.filename = arg
         else:
-            raise Exception('Unable to load image type %s' % str(type(arg)))
+            raise Exception('Unable to load image type {0!r}'.format(arg))
 
         # check if the image hase sequences for animation in it
         self._img_iterate()

kivy/properties.pyx

@@ -174,6 +174,7 @@ __all__ = ('Property',
 include "graphics/config.pxi"
 
 from weakref import ref
+from kivy.compat import string_types
 
 cdef float g_dpi = -1
 cdef float g_density = -1
@@ -491,16 +492,10 @@ cdef class StringProperty(Property):
     cdef check(self, EventDispatcher obj, value):
         if Property.check(self, obj, value):
             return True
-        IF PY3:
-            if not isinstance(value, str):
-                raise ValueError('%s.%s accept only str' % (
-                    obj.__class__.__name__,
-                    self.name))
-        ELSE:
-            if not isinstance(value, basestring):
-                raise ValueError('%s.%s accept only str/unicode' % (
-                    obj.__class__.__name__,
-                    self.name))
+        if not isinstance(value, string_types):
+            raise ValueError('%s.%s accept only str' % (
+                obj.__class__.__name__,
+                self.name))
 
 cdef inline void observable_list_dispatch(object self):
     cdef Property prop = self.prop

kivy/tests/test_adapters.py

@@ -22,6 +22,7 @@ from kivy.properties import StringProperty
 
 from kivy.factory import Factory
 from kivy.lang import Builder
+from kivy.compat import string_types
 
 from nose.tools import raises
 
@@ -490,7 +491,7 @@ class AdaptersTestCase(unittest.TestCase):
 
         cat_data_item = list_adapter.get_data_item(0)
         self.assertEqual(cat_data_item, 'cat')
-        self.assertTrue(isinstance(cat_data_item, str))
+        self.assertTrue(isinstance(cat_data_item, string_types))
 
         view = list_adapter.get_view(0)
         self.assertTrue(isinstance(view, ListItemButton))
@@ -670,7 +671,7 @@ class AdaptersTestCase(unittest.TestCase):
 
         cat_data_item = list_adapter.get_data_item(0)
         self.assertEqual(cat_data_item, 'cat')
-        self.assertTrue(isinstance(cat_data_item, str))
+        self.assertTrue(isinstance(cat_data_item, string_types))
 
         view = list_adapter.get_view(0)
         self.assertTrue(isinstance(view, ListItemButton))