Fix collections.abc deprecation warning for py 3.8

CHANGELOG.md

@@ -1,3 +1,7 @@
+## UNRELEASED
+## Fixed
+- Fixed collections.abc deprecation warning for python 3.8 [#563](https://github.com/plotly/dash/pull/563)
+
 ## [0.36.0] - 2019-01-25
 ## Removed
 - Removed support for `Event` system. Use event properties instead, for example the `n_clicks` property instead of the `click` event, see [#531](https://github.com/plotly/dash/issues/531) for details. `dash_renderer` MUST be upgraded to >=0.17.0 together with this, and it is recommended to update `dash_core_components` to >=0.43.0 and `dash_html_components` to >=0.14.0. [#550](https://github.com/plotly/dash/pull/550)

dash/_utils.py

@@ -1,4 +1,6 @@
 import uuid
+import collections
+import six
 
 
 def interpolate_str(template, **data):
@@ -40,6 +42,13 @@ def get_asset_path(
     ])
 
 
+# pylint: disable=no-member
+def patch_collections_abc(member):
+    if six.PY2:
+        return getattr(collections, member)
+    return getattr(collections.abc, member)
+
+
 class AttributeDict(dict):
     """
     Dictionary subclass enabling attribute lookup/assignment of keys/values.

dash/dash.py

@@ -30,8 +30,9 @@
 from ._utils import interpolate_str as _interpolate
 from ._utils import format_tag as _format_tag
 from ._utils import generate_hash as _generate_hash
-from . import _watch
 from ._utils import get_asset_path as _get_asset_path
+from ._utils import patch_collections_abc as _patch_collections_abc
+from . import _watch
 from . import _configs
 
 
@@ -275,7 +276,7 @@ def layout(self):
         return self._layout
 
     def _layout_value(self):
-        if isinstance(self._layout, collections.Callable):
+        if isinstance(self._layout, _patch_collections_abc('Callable')):
             self._cached_layout = self._layout()
         else:
             self._cached_layout = self._layout
@@ -284,7 +285,7 @@ def _layout_value(self):
     @layout.setter
     def layout(self, value):
         if (not isinstance(value, Component) and
-                not isinstance(value, collections.Callable)):
+                not isinstance(value, _patch_collections_abc('Callable'))):
             raise exceptions.NoLayoutException(
                 ''
                 'Layout must be a dash component '

dash/development/base_component.py

@@ -5,6 +5,8 @@
 
 import six
 
+from .._utils import patch_collections_abc
+
 
 # pylint: disable=no-init,too-few-public-methods
 class ComponentRegistry:
@@ -58,7 +60,7 @@ def _check_if_has_indexable_children(item):
 
 
 @six.add_metaclass(ComponentMeta)
-class Component(collections.MutableMapping):
+class Component(patch_collections_abc('MutableMapping')):
     class _UNDEFINED(object):
         def __repr__(self):
             return 'undefined'