Merge pull request #892 from plotly/py23

⚗️ try with future collections:

Author: byronz

CONTRIBUTING.md

@@ -42,6 +42,14 @@ As of Dash 1.2, the renderer bundle and its peer dependencies can be packed and
 
 When a change in renderer code doesn't reflect in your browser as expected, this could be: confused bundle generation, caching issue in a browser, python package not in `editable` mode, etc. The new tool reduces the risk of bundle assets by adding the digest to help compare asset changes.
 
+## Python 2 And 3 Compatibility
+
+Writing Python 2/3 compatible code might be a challenging task for contributors used to working on one particular version, especially new learners who start directly with Python 3.
+
+From the #892, we started to adopt  `python-future`  instead of  `six`  as our tool to better achieve the goal where we can mainly write Python 3 code and make it back-compatible in Python 2.7 (last Python 2 version Dash supports before it gets deprecated).
+
+Please refer to [this list of idioms](https://python-future.org/compatible_idioms.html "https://python-future.org/compatible_idioms.html") for more details on working with `python-future`.
+
 ## Git
 
 Use the [GitHub flow](https://guides.github.com/introduction/flow/) when proposing contributions to this repository (i.e. create a feature branch and submit a PR against the default branch).

dash/_utils.py

@@ -9,8 +9,7 @@
 import logging
 from io import open  # pylint: disable=redefined-builtin
 from functools import wraps
-
-import six
+import future.utils as utils
 
 logger = logging.getLogger()
 
@@ -57,9 +56,7 @@ def get_asset_path(requests_pathname, asset_path, asset_url_path):
 
 # pylint: disable=no-member
 def patch_collections_abc(member):
-    if six.PY2:
-        return getattr(collections, member)
-    return getattr(collections.abc, member)
+    return getattr(collections if utils.PY2 else collections.abc, member)
 
 
 class AttributeDict(dict):
@@ -145,8 +142,8 @@ def run_command_with_process(cmd):
 
 
 def compute_md5(path):
-    with open(path, encoding='utf-8') as fp:
-        return hashlib.md5(fp.read().encode('utf-8')).hexdigest()
+    with open(path, encoding="utf-8") as fp:
+        return hashlib.md5(fp.read().encode("utf-8")).hexdigest()
 
 
 def job(msg=""):
@@ -157,5 +154,7 @@ def _wrapper(*args, **kwargs):
             res = func(*args, **kwargs)
             logger.info("::: 🍻🍻🍻 [%s] job done 🍻🍻🍻 :::", func.__name__)
             return res
+
         return _wrapper
+
     return wrapper

dash/dash.py

@@ -17,7 +17,6 @@
 from textwrap import dedent
 
 import flask
-from flask import Flask, Response
 from flask_compress import Compress
 from werkzeug.debug.tbtools import get_current_traceback
 
@@ -241,13 +240,13 @@ def __init__(
 
         # We have 3 cases: server is either True (we create the server), False
         # (defer server creation) or a Flask app instance (we use their server)
-        if isinstance(server, Flask):
+        if isinstance(server, flask.Flask):
             self.server = server
             if name is None:
                 name = getattr(server, 'name', '__main__')
         elif isinstance(server, bool):
             name = name if name else '__main__'
-            self.server = Flask(name) if server else None
+            self.server = flask.Flask(name) if server else None
         else:
             raise ValueError('server must be a Flask app or a boolean')
 
@@ -677,7 +676,7 @@ def serve_component_suites(self, package_name, path_in_package_dist):
             'map': 'application/json'
         })[path_in_package_dist.split('.')[-1]]
 
-        return Response(
+        return flask.Response(
             pkgutil.get_data(package_name, path_in_package_dist),
             mimetype=mimetype
         )