Add util.copy_with. (#2562)

src/gluonts/util.py

@@ -11,8 +11,36 @@
 # express or implied. See the License for the specific language governing
 # permissions and limitations under the License.
 
+import copy
 from functools import lru_cache
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, TypeVar
+
+T = TypeVar("T")
+
+
+def copy_with(obj: T, **kwargs) -> T:
+    """Return copy of `obj` and update attributes of the copy using `kwargs`.
+
+    ::
+
+        @dataclass
+        class MyClass:
+            value: int
+
+        a = MyClass(1)
+        b = copy_with(a, value=2)
+
+        assert a.value == 1
+        assert b.value == 2
+
+    """
+
+    new_obj = copy.copy(obj)
+
+    for name, value in kwargs.items():
+        setattr(new_obj, name, value)
+
+    return new_obj
 
 
 if TYPE_CHECKING:

test/__init__.py

@@ -0,0 +1,12 @@
+# Copyright 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License").
+# You may not use this file except in compliance with the License.
+# A copy of the License is located at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# or in the "license" file accompanying this file. This file is distributed
+# on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+# express or implied. See the License for the specific language governing
+# permissions and limitations under the License.

test/test_util.py

@@ -0,0 +1,26 @@
+# Copyright 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License").
+# You may not use this file except in compliance with the License.
+# A copy of the License is located at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# or in the "license" file accompanying this file. This file is distributed
+# on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+# express or implied. See the License for the specific language governing
+# permissions and limitations under the License.
+
+from gluonts.util import copy_with
+
+
+def test_copy_with():
+    class X:
+        def __init__(self, value):
+            self.value = value
+
+    a = X(42)
+    b = copy_with(a, value=99)
+
+    assert a.value == 42
+    assert b.value == 99