Github user zentol commented on a diff in the pull request:
https://github.com/apache/flink/pull/3838#discussion_r117724247
--- Diff:
flink-libraries/flink-streaming-python/src/main/java/org/apache/flink/streaming/python/api/datastream/PythonDataStream.java
---
@@ -0,0 +1,262 @@
+/*
+ * 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.
+ */
+package org.apache.flink.streaming.python.api.datastream;
+
+import org.apache.flink.annotation.Public;
+import org.apache.flink.annotation.PublicEvolving;
+import org.apache.flink.api.common.functions.FilterFunction;
+import org.apache.flink.api.common.functions.FlatMapFunction;
+import org.apache.flink.api.common.functions.MapFunction;
+import org.apache.flink.api.java.functions.KeySelector;
+import org.apache.flink.core.fs.FileSystem.WriteMode;
+import org.apache.flink.streaming.api.collector.selector.OutputSelector;
+import org.apache.flink.streaming.api.datastream.DataStream;
+import
org.apache.flink.streaming.api.datastream.SingleOutputStreamOperator;
+import org.apache.flink.streaming.api.functions.sink.SinkFunction;
+import org.apache.flink.streaming.python.api.functions.PyKey;
+import
org.apache.flink.streaming.python.api.functions.PythonFilterFunction;
+import
org.apache.flink.streaming.python.api.functions.PythonFlatMapFunction;
+import org.apache.flink.streaming.python.api.functions.PythonKeySelector;
+import org.apache.flink.streaming.python.api.functions.PythonMapFunction;
+import
org.apache.flink.streaming.python.api.functions.PythonOutputSelector;
+import org.apache.flink.streaming.python.api.functions.PythonSinkFunction;
+import
org.apache.flink.streaming.python.util.serialization.PythonSerializationSchema;
+import org.apache.flink.streaming.util.serialization.SerializationSchema;
+import org.python.core.PyObject;
+
+import java.io.IOException;
+import java.util.ArrayList;
+
+
+/**
+ * A {@code PythonDataStream} is a thin wrapper layer over {@link
DataStream}, which represents a
+ * stream of elements of the same type. A {@code PythonDataStream} can be
transformed into
+ * another {@code PythonDataStream} by applying various transformation
functions, such as
+ * <ul>
+ * <li>{@link PythonDataStream#map}
+ * <li>{@link PythonDataStream#split}
+ * </ul>
+ *
+ * <p>A thin wrapper layer means that the functionality itself is
performed by the
+ * {@link DataStream}, however instead of working directly with the
streaming data sets,
+ * this layer handles Python wrappers (e.g. {@code PythonDataStream}) to
comply with the
+ * Python standard coding styles.</p>
+ */
+@Public
+public class PythonDataStream<D extends DataStream<PyObject>> {
+ protected final D stream;
+
+ public PythonDataStream(D stream) {
+ this.stream = stream;
+ }
+
+ /**
+ * A thin wrapper layer over {@link DataStream#union(DataStream[])}.
+ *
+ * @param streams
+ * The Python DataStreams to union output with.
+ * @return The {@link PythonDataStream}.
+ */
+ @SafeVarargs
+ @SuppressWarnings("unchecked")
+ public final PythonDataStream union(PythonDataStream... streams) {
+ ArrayList<DataStream<PyObject>> dsList = new ArrayList<>();
+ for (PythonDataStream ps : streams) {
+ dsList.add(ps.stream);
+ }
+ DataStream<PyObject>[] dsArray = new DataStream[dsList.size()];
+ return new
PythonDataStream(stream.union(dsList.toArray(dsArray)));
+ }
+
+ /**
+ * A thin wrapper layer over {@link DataStream#split(OutputSelector)}.
+ *
+ * @param output_selector
+ * The user defined {@link OutputSelector} for directing the
tuples.
+ * @return The {@link PythonSplitStream}
+ */
+ public PythonSplitStream split(OutputSelector<PyObject>
output_selector) throws IOException {
+ return new PythonSplitStream(this.stream.split(new
PythonOutputSelector(output_selector)));
+ }
+
+ /**
+ * A thin wrapper layer over {@link DataStream#filter(FilterFunction)}.
+ *
+ * @param filter
+ * The FilterFunction that is called for each element of the
DataStream.
+ * @return The filtered {@link PythonDataStream}.
+ */
+ public PythonSingleOutputStreamOperator filter(FilterFunction<PyObject>
filter) throws IOException {
+ return new PythonSingleOutputStreamOperator(stream.filter(new
PythonFilterFunction(filter)));
+ }
+
+ /**
+ * A thin wrapper layer over {@link DataStream#map(MapFunction)}.
+ *
+ * @param mapper
+ * The MapFunction that is called for each element of the
+ * DataStream.
+ * @return The transformed {@link PythonDataStream}.
+ */
+ public PythonDataStream<SingleOutputStreamOperator<PyObject>> map(
+ MapFunction<PyObject, PyObject> mapper) throws IOException {
+ return new PythonDataStream<>(stream.map(new
PythonMapFunction(mapper)));
+ }
+
+ /**
+ * A thin wrapper layer over {@link
DataStream#flatMap(FlatMapFunction)}.
+ *
+ * @param flat_mapper
+ * The FlatMapFunction that is called for each element of the
+ * DataStream
+ *
+ * @return The transformed {@link PythonDataStream}.
+ */
+ public PythonDataStream<SingleOutputStreamOperator<PyObject>> flat_map(
+ FlatMapFunction<PyObject, PyObject> flat_mapper) throws
IOException {
+ return new PythonDataStream<>(stream.flatMap(new
PythonFlatMapFunction(flat_mapper)));
+ }
+
+ /**
+ * A thin wrapper layer over {@link DataStream#keyBy(KeySelector)}.
+ *
+ * @param selector
+ * The KeySelector to be used for extracting the key for
partitioning
+ * @return The {@link PythonDataStream} with partitioned state (i.e.
{@link PythonKeyedStream})
+ */
+ public PythonKeyedStream key_by(KeySelector<PyObject, PyKey> selector)
throws IOException {
+ return new PythonKeyedStream(stream.keyBy(new
PythonKeySelector(selector)));
+ }
+
+ /**
+ * A thin wrapper layer over {@link DataStream#print()}.
+ */
+ @PublicEvolving
+ public void print() { stream.print(); }
+
+ /**
+ * A thin wrapper layer over {@link
DataStream#writeAsText(java.lang.String)}.
+ *
+ * @param path
+ * The path pointing to the location the text file is
written to.
+ */
+ @PublicEvolving
+ public void write_as_text(String path) { stream.writeAsText(path); }
--- End diff --
`stream.print();` should be on a separate line.
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