Get config item if variable is None

dask/config.py

@@ -423,10 +423,13 @@ def refresh(config=config, defaults=defaults, **kwargs):
     update(config, collect(**kwargs))
 
 
-def get(key, default=no_default, config=config):
+def get(key, default=no_default, config=config, override_with=None):
     """
     Get elements from global config
 
+    If ``override_with`` is not None this value will be passed straight back.
+    Useful for getting kwarg defaults from Dask config.
+
     Use '.' for nested access
 
     Examples
@@ -441,10 +444,18 @@ def get(key, default=no_default, config=config):
     >>> config.get('foo.x.y', default=123)  # doctest: +SKIP
     123
 
+    >>> config.get('foo.y', override_with=None)  # doctest: +SKIP
+    2
+
+    >>> config.get('foo.y', override_with=3)  # doctest: +SKIP
+    3
+
     See Also
     --------
     dask.config.set
     """
+    if override_with is not None:
+        return override_with
     keys = key.split(".")
     result = config
     for k in keys:

dask/tests/test_config.py

@@ -472,3 +472,20 @@ def test_deprecations():
             assert dask.config.get("optimization.fuse.ave-width") == 123
 
     assert "optimization.fuse.ave-width" in str(info[0].message)
+
+
+def test_get_override_with():
+    with dask.config.set({"foo": "bar"}):
+        # If override_with is None get the config key
+        assert dask.config.get("foo") == "bar"
+        assert dask.config.get("foo", override_with=None) == "bar"
+
+        # Otherwise pass the default straight through
+        assert dask.config.get("foo", override_with="baz") == "baz"
+        assert dask.config.get("foo", override_with=False) is False
+        assert dask.config.get("foo", override_with=True) is True
+        assert dask.config.get("foo", override_with=123) == 123
+        assert dask.config.get("foo", override_with={"hello": "world"}) == {
+            "hello": "world"
+        }
+        assert dask.config.get("foo", override_with=["one"]) == ["one"]