[SPARK-35499][PYTHON] Apply black to pandas API on Spark codes

### What changes were proposed in this pull request?

This PR proposes applying `black` to pandas API on Spark codes, for improving static analysis.

By executing the `./dev/reformat-python` in the spark home directory, all the code of the pandas API on Spark is fixed according to the static analysis rules.

### Why are the changes needed?

This can be reduces the cost of static analysis during development.

It has been used continuously for about a year in the Koalas project and its convenience has been proven.

### Does this PR introduce _any_ user-facing change?

No, it's dev-only.

### How was this patch tested?

Manually reformat the pandas API on Spark codes by running the `./dev/reformat-python`, and checked the `./dev/lint-python` is passed.

Closes #32779 from itholic/SPARK-35499.

Authored-by: itholic <[email protected]>
Signed-off-by: Liang-Chi Hsieh <[email protected]>

Author: itholic

.github/workflows/build_and_test.yml

@@ -366,7 +366,7 @@ jobs:
         #   See also https://github.com/sphinx-doc/sphinx/issues/7551.
         # Jinja2 3.0.0+ causes error when building with Sphinx.
         #   See also https://issues.apache.org/jira/browse/SPARK-35375.
-        python3.6 -m pip install flake8 pydata_sphinx_theme mypy numpydoc 'jinja2<3.0.0'
+        python3.6 -m pip install flake8 pydata_sphinx_theme mypy numpydoc 'jinja2<3.0.0' 'black==21.5b2'
     - name: Install R linter dependencies and SparkR
       run: |
         apt-get install -y libcurl4-openssl-dev libgit2-dev libssl-dev libxml2-dev

dev/lint-python

@@ -25,6 +25,8 @@ MINIMUM_PYCODESTYLE="2.7.0"
 
 PYTHON_EXECUTABLE="python3"
 
+BLACK_BUILD="$PYTHON_EXECUTABLE -m black"
+
 function satisfies_min_version {
     local provided_version="$1"
     local expected_version="$2"
@@ -185,6 +187,35 @@ flake8 checks failed."
     fi
 }
 
+function black_test {
+    local BLACK_REPORT=
+    local BLACK_STATUS=
+
+    # Skip check if black is not installed.
+    $BLACK_BUILD 2> /dev/null
+    if [ $? -ne 0 ]; then
+        echo "The $BLACK_BUILD command was not found. Skipping black checks for now."
+        echo
+        return
+    fi
+
+    echo "starting black test..."
+    # Black is only applied for pandas API on Spark for now.
+    BLACK_REPORT=$( ($BLACK_BUILD python/pyspark/pandas --line-length 100 --check ) 2>&1)
+    BLACK_STATUS=$?
+
+    if [ "$BLACK_STATUS" -ne 0 ]; then
+        echo "black checks failed:"
+        echo "$BLACK_REPORT"
+        echo "Please run 'dev/reformat-python' script."
+        echo "$BLACK_STATUS"
+        exit "$BLACK_STATUS"
+    else
+        echo "black checks passed."
+        echo
+    fi
+}
+
 SCRIPT_DIR="$( cd "$( dirname "$0" )" && pwd )"
 SPARK_ROOT_DIR="$(dirname "${SCRIPT_DIR}")"
 
@@ -194,6 +225,7 @@ pushd "$SPARK_ROOT_DIR" &> /dev/null
 PYTHON_SOURCE="$(find . -path ./docs/.local_ruby_bundle -prune -false -o -name "*.py")"
 
 compile_python_test "$PYTHON_SOURCE"
+black_test
 pycodestyle_test "$PYTHON_SOURCE"
 flake8_test
 mypy_test

dev/reformat-python

@@ -0,0 +1,32 @@
+#!/usr/bin/env bash
+#
+# 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.
+
+# The current directory of the script.
+DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
+FWDIR="$( cd "$DIR"/.. && pwd )"
+cd "$FWDIR"
+
+BLACK_BUILD="python -m black"
+BLACK_VERSION="21.5b2"
+$BLACK_BUILD 2> /dev/null
+if [ $? -ne 0 ]; then
+    echo "The '$BLACK_BUILD' command was not found. Please install Black, for example, via 'pip install black==$BLACK_VERSION'."
+    exit 1
+fi
+
+# This script is only applied for pandas API on Spark for now.
+$BLACK_BUILD python/pyspark/pandas --line-length 100

dev/requirements.txt

@@ -32,3 +32,6 @@ sphinx-plotly-directive
 # Development scripts
 jira
 PyGithub
+
+# pandas API on Spark Code formatter.
+black

dev/tox.ini

@@ -14,11 +14,13 @@
 # limitations under the License.
 
 [pycodestyle]
-ignore=E226,E241,E305,E402,E722,E731,E741,W503,W504
+ignore=E203,E226,E241,E305,E402,E722,E731,E741,W503,W504
 max-line-length=100
 exclude=*/target/*,python/pyspark/cloudpickle/*.py,shared.py,python/docs/source/conf.py,work/*/*.py,python/.eggs/*,dist/*,.git/*
 
 [flake8]
 select = E901,E999,F821,F822,F823,F401,F405,B006
+# Ignore F821 for plot documents in pandas API on Spark.
+ignore = F821
 exclude = python/docs/build/html/*,*/target/*,python/pyspark/cloudpickle/*.py,shared.py*,python/docs/source/conf.py,work/*/*.py,python/.eggs/*,dist/*,.git/*,python/out,python/pyspark/sql/pandas/functions.pyi,python/pyspark/sql/column.pyi,python/pyspark/worker.pyi,python/pyspark/java_gateway.pyi
 max-line-length = 100

python/pyspark/pandas/accessors.py

@@ -48,7 +48,7 @@
 
 
 class PandasOnSparkFrameMethods(object):
-    """ pandas-on-Spark specific features for DataFrame. """
+    """pandas-on-Spark specific features for DataFrame."""
 
     def __init__(self, frame: "DataFrame"):
         self._psdf = frame
@@ -696,7 +696,7 @@ def pandas_frame_func(f, field_name):
 
 
 class PandasOnSparkSeriesMethods(object):
-    """ pandas-on-Spark specific features for Series. """
+    """pandas-on-Spark specific features for Series."""
 
     def __init__(self, series: "Series"):
         self._psser = series

python/pyspark/pandas/base.py

@@ -1068,9 +1068,7 @@ def notnull(self) -> Union["Series", "Index"]:
 
         if isinstance(self, MultiIndex):
             raise NotImplementedError("notna is not defined for MultiIndex")
-        return (~self.isnull()).rename(
-            self.name  # type: ignore
-        )
+        return (~self.isnull()).rename(self.name)  # type: ignore
 
     notna = notnull
 

python/pyspark/pandas/config.py

@@ -381,7 +381,7 @@ def _check_option(key: str) -> None:
 
 
 class DictWrapper:
-    """ provide attribute-style access to a nested dict"""
+    """provide attribute-style access to a nested dict"""
 
     def __init__(self, d: Dict[str, Option], prefix: str = ""):
         object.__setattr__(self, "d", d)

python/pyspark/pandas/data_type_ops/base.py

@@ -45,11 +45,7 @@
     from pyspark.pandas.series import Series  # noqa: F401 (SPARK-34943)
 
 
-def is_valid_operand_for_numeric_arithmetic(
-    operand: Any,
-    *,
-    allow_bool: bool = True
-) -> bool:
+def is_valid_operand_for_numeric_arithmetic(operand: Any, *, allow_bool: bool = True) -> bool:
     """Check whether the operand is valid for arithmetic operations against numerics."""
     if isinstance(operand, numbers.Number) and not isinstance(operand, bool):
         return True
@@ -58,7 +54,8 @@ def is_valid_operand_for_numeric_arithmetic(
             return False
         else:
             return isinstance(operand.spark.data_type, NumericType) or (
-                allow_bool and isinstance(operand.spark.data_type, BooleanType))
+                allow_bool and isinstance(operand.spark.data_type, BooleanType)
+            )
     else:
         return False
 

python/pyspark/pandas/data_type_ops/binary_ops.py

@@ -34,7 +34,7 @@ class BinaryOps(DataTypeOps):
 
     @property
     def pretty_name(self) -> str:
-        return 'binaries'
+        return "binaries"
 
     def add(self, left, right) -> Union["Series", "Index"]:
         if isinstance(right, IndexOpsMixin) and isinstance(right.spark.data_type, BinaryType):
@@ -43,11 +43,13 @@ def add(self, left, right) -> Union["Series", "Index"]:
             return column_op(F.concat)(left, F.lit(right))
         else:
             raise TypeError(
-                "Concatenation can not be applied to %s and the given type." % self.pretty_name)
+                "Concatenation can not be applied to %s and the given type." % self.pretty_name
+            )
 
     def radd(self, left, right) -> Union["Series", "Index"]:
         if isinstance(right, bytes):
             return left._with_new_scol(F.concat(F.lit(right), left.spark.column))
         else:
             raise TypeError(
-                "Concatenation can not be applied to %s and the given type." % self.pretty_name)
+                "Concatenation can not be applied to %s and the given type." % self.pretty_name
+            )