refactor: decouple pandas postprocessing operator (#18710)

superset/utils/pandas_postprocessing/diff.py

@@ -0,0 +1,51 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License 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 typing import Dict
+
+from pandas import DataFrame
+
+from superset.constants import PandasAxis
+from superset.utils.pandas_postprocessing.utils import (
+    _append_columns,
+    validate_column_args,
+)
+
+
+@validate_column_args("columns")
+def diff(
+    df: DataFrame,
+    columns: Dict[str, str],
+    periods: int = 1,
+    axis: PandasAxis = PandasAxis.ROW,
+) -> DataFrame:
+    """
+    Calculate row-by-row or column-by-column difference for select columns.
+
+    :param df: DataFrame on which the diff will be based.
+    :param columns: columns on which to perform diff, mapping source column to
+           target column. For instance, `{'y': 'y'}` will replace the column `y` with
+           the diff value in `y`, while `{'y': 'y2'}` will add a column `y2` based
+           on diff values calculated from `y`, leaving the original column `y`
+           unchanged.
+    :param periods: periods to shift for calculating difference.
+    :param axis: 0 for row, 1 for column. default 0.
+    :return: DataFrame with diffed columns
+    :raises QueryObjectValidationError: If the request in incorrect
+    """
+    df_diff = df[columns.keys()]
+    df_diff = df_diff.diff(periods=periods, axis=axis)
+    return _append_columns(df, df_diff, columns)