在Pyspark中如何在列表中添加所有值？

流浪者

我正在jupyter笔记本中运行以下pyspark转换。我的要求是在元素中添加所有值，例如469 + 84451 + 903 ...，并且应该只返回总数。

以下是转换和操作：

In [46]: newdispokey1.collect()

[(u'Hello', 469),
 (u'is', 84451),
 (u'the', 903),
 (u'an', 21208),
 (u'and', 19903),
 (u'route', 185),
 (u'bag', 1894),
 (u'metal', 315),
 (u'bus', 620194),
 (u'cloud', 1036)]

预期结果是所有值的加法。我正在尝试以下转换和操作：

   In [46]: newdispokey1.reduce( lambda x,y: x[1]+y[1] ).collect()

并得到错误。

    ---------------------------------------------------------------------------
Py4JJavaError                             Traceback (most recent call last)
<ipython-input-46-9557bb70b499> in <module>()
----> 1 newdispokey1.reduce( lambda x,y: x[1]+y[1] ).collect()

/home/newuser/spark/python/pyspark/rdd.pyc in reduce(self, f)
    797             yield reduce(f, iterator, initial)
    798 
--> 799         vals = self.mapPartitions(func).collect()
    800         if vals:
    801             return reduce(f, vals)

/home/newuser/spark/python/pyspark/rdd.pyc in collect(self)
    772         with SCCallSiteSync(self.context) as css:
--> 773             port = self.ctx._jvm.PythonRDD.collectAndServe(self._jrdd.rdd())
    774         return list(_load_from_socket(port, self._jrdd_deserializer))
    775 

/home/newuser/spark/python/lib/py4j-0.8.2.1-src.zip/py4j/java_gateway.py in __call__(self, *args)
    536         answer = self.gateway_client.send_command(command)
    537         return_value = get_return_value(answer, self.gateway_client,
--> 538                 self.target_id, self.name)
    539 
    540         for temp_arg in temp_args:

/home/newuser/spark/python/pyspark/sql/utils.pyc in deco(*a, **kw)
     34     def deco(*a, **kw):
     35         try:
---> 36             return f(*a, **kw)
     37         except py4j.protocol.Py4JJavaError as e:
     38             s = e.java_exception.toString()

/home/newuser/spark/python/lib/py4j-0.8.2.1-src.zip/py4j/protocol.py in get_return_value(answer, gateway_client, target_id, name)
    298                 raise Py4JJavaError(
    299                     'An error occurred while calling {0}{1}{2}.\n'.
--> 300                     format(target_id, '.', name), value)
    301             else:
    302                 raise Py4JError(

Py4JJavaError: An error occurred while calling z:org.apache.spark.api.python.PythonRDD.collectAndServe.
: org.apache.spark.SparkException: Job aborted due to stage failure: Task 0 in stage 48.0 failed 1 times, most recent failure: Lost task 0.0 in stage 48.0 (TID 167, localhost): org.apache.spark.api.python.PythonException: Traceback (most recent call last):
  File "/home/newuser/spark/python/lib/pyspark.zip/pyspark/worker.py", line 111, in main
    process()
  File "/home/newuser/spark/python/lib/pyspark.zip/pyspark/worker.py", line 106, in process
    serializer.dump_stream(func(split_index, iterator), outfile)
  File "/home/newuser/spark/python/lib/pyspark.zip/pyspark/serializers.py", line 263, in dump_stream
    vs = list(itertools.islice(iterator, batch))
  File "/home/newuser/spark/python/pyspark/rdd.py", line 797, in func
    yield reduce(f, iterator, initial)
  File "<ipython-input-46-9557bb70b499>", line 1, in <lambda>
TypeError: 'int' object has no attribute '__getitem__'

    at org.apache.spark.api.python.PythonRunner$$anon$1.read(PythonRDD.scala:166)
    at org.apache.spark.api.python.PythonRunner$$anon$1.<init>(PythonRDD.scala:207)
    at org.apache.spark.api.python.PythonRunner.compute(PythonRDD.scala:125)
    at org.apache.spark.api.python.PythonRDD.compute(PythonRDD.scala:70)
    at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:300)
    at org.apache.spark.rdd.RDD.iterator(RDD.scala:264)
    at org.apache.spark.scheduler.ResultTask.runTask(ResultTask.scala:66)
    at org.apache.spark.scheduler.Task.run(Task.scala:88)
    at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:214)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)

Driver stacktrace:
    at org.apache.spark.scheduler.DAGScheduler.org$apache$spark$scheduler$DAGScheduler$$failJobAndIndependentStages(DAGScheduler.scala:1283)
    at org.apache.spark.scheduler.DAGScheduler$$anonfun$abortStage$1.apply(DAGScheduler.scala:1271)
    at org.apache.spark.scheduler.DAGScheduler$$anonfun$abortStage$1.apply(DAGScheduler.scala:1270)
    at scala.collection.mutable.ResizableArray$class.foreach(ResizableArray.scala:59)
    at scala.collection.mutable.ArrayBuffer.foreach(ArrayBuffer.scala:47)
    at org.apache.spark.scheduler.DAGScheduler.abortStage(DAGScheduler.scala:1270)
    at org.apache.spark.scheduler.DAGScheduler$$anonfun$handleTaskSetFailed$1.apply(DAGScheduler.scala:697)
    at org.apache.spark.scheduler.DAGScheduler$$anonfun$handleTaskSetFailed$1.apply(DAGScheduler.scala:697)
    at scala.Option.foreach(Option.scala:236)
    at org.apache.spark.scheduler.DAGScheduler.handleTaskSetFailed(DAGScheduler.scala:697)
    at org.apache.spark.scheduler.DAGSchedulerEventProcessLoop.doOnReceive(DAGScheduler.scala:1496)
    at org.apache.spark.scheduler.DAGSchedulerEventProcessLoop.onReceive(DAGScheduler.scala:1458)
    at org.apache.spark.scheduler.DAGSchedulerEventProcessLoop.onReceive(DAGScheduler.scala:1447)
    at org.apache.spark.util.EventLoop$$anon$1.run(EventLoop.scala:48)
    at org.apache.spark.scheduler.DAGScheduler.runJob(DAGScheduler.scala:567)
    at org.apache.spark.SparkContext.runJob(SparkContext.scala:1824)
    at org.apache.spark.SparkContext.runJob(SparkContext.scala:1837)
    at org.apache.spark.SparkContext.runJob(SparkContext.scala:1850)
    at org.apache.spark.SparkContext.runJob(SparkContext.scala:1921)
    at org.apache.spark.rdd.RDD$$anonfun$collect$1.apply(RDD.scala:909)
    at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:147)
    at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:108)
    at org.apache.spark.rdd.RDD.withScope(RDD.scala:310)
    at org.apache.spark.rdd.RDD.collect(RDD.scala:908)
    at org.apache.spark.api.python.PythonRDD$.collectAndServe(PythonRDD.scala:405)
    at org.apache.spark.api.python.PythonRDD.collectAndServe(PythonRDD.scala)
    at sun.reflect.GeneratedMethodAccessor46.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at py4j.reflection.MethodInvoker.invoke(MethodInvoker.java:231)
    at py4j.reflection.ReflectionEngine.invoke(ReflectionEngine.java:379)
    at py4j.Gateway.invoke(Gateway.java:259)
    at py4j.commands.AbstractCommand.invokeMethod(AbstractCommand.java:133)
    at py4j.commands.CallCommand.execute(CallCommand.java:79)
    at py4j.GatewayConnection.run(GatewayConnection.java:207)
    at java.lang.Thread.run(Thread.java:745)
Caused by: org.apache.spark.api.python.PythonException: Traceback (most recent call last):
  File "/home/newuser/spark/python/lib/pyspark.zip/pyspark/worker.py", line 111, in main
    process()
  File "/home/newuser/spark/python/lib/pyspark.zip/pyspark/worker.py", line 106, in process
    serializer.dump_stream(func(split_index, iterator), outfile)
  File "/home/newuser/spark/python/lib/pyspark.zip/pyspark/serializers.py", line 263, in dump_stream
    vs = list(itertools.islice(iterator, batch))
  File "/home/newuser/spark/python/pyspark/rdd.py", line 797, in func
    yield reduce(f, iterator, initial)
  File "<ipython-input-46-9557bb70b499>", line 1, in <lambda>
TypeError: 'int' object has no attribute '__getitem__'

    at org.apache.spark.api.python.PythonRunner$$anon$1.read(PythonRDD.scala:166)
    at org.apache.spark.api.python.PythonRunner$$anon$1.<init>(PythonRDD.scala:207)
    at org.apache.spark.api.python.PythonRunner.compute(PythonRDD.scala:125)
    at org.apache.spark.api.python.PythonRDD.compute(PythonRDD.scala:70)
    at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:300)
    at org.apache.spark.rdd.RDD.iterator(RDD.scala:264)
    at org.apache.spark.scheduler.ResultTask.runTask(ResultTask.scala:66)
    at org.apache.spark.scheduler.Task.run(Task.scala:88)
    at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:214)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    ... 1 more

我是Apache Spark的新手，如何解决此问题？

埃拉扎尔

最简单的解决方案是

>>> newdispokey1.values().sum()
750558

问题在于reduce方法的参数类型-减速器的类型。它接收两个元素：一个是前一个结果，或者第一个元素，第二个是新元素。因此，您必须返回一个看起来与其他任何元素一样的元素-您必须返回一个对：

>>> newdispokey1.reduce(lambda x, y: ('', x[1] + y[1]))
('', 750558)

或更详细地说明，以防您要更改此内容：

>>> newdispokey1.map(lambda x: x[1]).reduce(lambda x, y: x + y)
750558

与第一个解决方案等效（但可读性较差）。

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编辑于 2021-04-27

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