我有一个我编写的模块，其中包含作用于 PySpark DataFrames 的函数。他们对 DataFrame 中的列进行转换，然后返回一个新的 DataFrame。以下是代码示例，缩短为仅包含其中一个功能：
from pyspark.sql import functions as F
from pyspark.sql import types as t
import pandas as pd
import numpy as np
metadta=pd.DataFrame(pd.read_csv("metadata.csv")) # this contains metadata on my dataset
def str2num(text):
if type(text)==None or text=='' or text=='NULL' or text=='null':
return 0
elif len(text)==1:
return ord(text)
else:
newnum=''
for lettr in text:
newnum=newnum+str(ord(lettr))
return int(newnum)
str2numUDF = F.udf(lambda s: str2num(s), t.IntegerType())
def letConvNum(df): # df is a PySpark DataFrame
#Get a list of columns that I want to transform, using the metadata Pandas DataFrame
chng_cols=metadta[(metadta.comments=='letter conversion to num')].col_name.tolist()
for curcol in chng_cols:
df=df.withColumn(curcol, str2numUDF(df[curcol]))
return df
这就是我的模块，称之为 mymodule.py。如果我启动 PySpark shell，然后执行以下操作：
import mymodule as mm
myf=sqlContext.sql("select * from tablename lim 10")
我检查了 myf（PySpark DataFrame），没问题。我通过尝试使用 str2num 函数来检查我是否实际导入了 mymodule：
mm.str2num('a')
97
所以它实际上是在导入模块。然后，如果我尝试这个：
df2=mm.letConvNum(df)
并这样做以检查它是否有效：
df2.show()
它尝试执行该操作，但随后崩溃：
16/03/10 16:10:44 ERROR Executor: Exception in task 0.0 in stage 1.0 (TID 365)
org.apache.spark.api.python.PythonException: Traceback (most recent call last):
File "/usr/hdp/2.3.4.0-3485/spark/python/lib/pyspark.zip/pyspark/worker.py", line 98, in main
command = pickleSer._read_with_length(infile)
File "/usr/hdp/2.3.4.0-3485/spark/python/lib/pyspark.zip/pyspark/serializers.py", line 164, in _read_with_length
return self.loads(obj)
File "/usr/hdp/2.3.4.0-3485/spark/python/lib/pyspark.zip/pyspark/serializers.py", line 422, in loads
return pickle.loads(obj)
File "test2.py", line 16, in <module>
str2numUDF=F.udf(lambda s: str2num(s), t.IntegerType())
File "/usr/hdp/2.3.4.0-3485/spark/python/lib/pyspark.zip/pyspark/sql/functions.py", line 1460, in udf
return UserDefinedFunction(f, returnType)
File "/usr/hdp/2.3.4.0-3485/spark/python/lib/pyspark.zip/pyspark/sql/functions.py", line 1422, in __init__
self._judf = self._create_judf(name)
File "/usr/hdp/2.3.4.0-3485/spark/python/lib/pyspark.zip/pyspark/sql/functions.py", line 1430, in _create_judf
pickled_command, broadcast_vars, env, includes = _prepare_for_python_RDD(sc, command, self)
File "/usr/hdp/2.3.4.0-3485/spark/python/lib/pyspark.zip/pyspark/rdd.py", line 2317, in _prepare_for_python_RDD
[x._jbroadcast for x in sc._pickled_broadcast_vars],
AttributeError: 'NoneType' object has no attribute '_pickled_broadcast_vars'
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.sql.execution.BatchPythonEvaluation$$anonfun$doExecute$1.apply(python.scala:397)
at org.apache.spark.sql.execution.BatchPythonEvaluation$$anonfun$doExecute$1.apply(python.scala:362)
at org.apache.spark.rdd.RDD$$anonfun$mapPartitions$1$$anonfun$apply$17.apply(RDD.scala:710)
at org.apache.spark.rdd.RDD$$anonfun$mapPartitions$1$$anonfun$apply$17.apply(RDD.scala:710)
at org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:38)
at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:300)
at org.apache.spark.rdd.RDD.iterator(RDD.scala:264)
at org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:38)
at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:300)
at org.apache.spark.rdd.RDD.iterator(RDD.scala:264)
at org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:38)
at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:300)
at org.apache.spark.rdd.RDD.iterator(RDD.scala:264)
at org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:38)
at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:300)
at org.apache.spark.rdd.RDD.iterator(RDD.scala:264)
at org.apache.spark.scheduler.ResultTask.runTask(ResultTask.scala:66)
at org.apache.spark.scheduler.Task.run(Task.scala:88)
at org.apache.spark.executor.Executor$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)
16/03/10 16:10:44 ERROR TaskSetManager: Task 0 in stage 1.0 failed 1 times; aborting job
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/hdp/2.3.4.0-3485/spark/python/pyspark/sql/dataframe.py", line 256, in show
print(self._jdf.showString(n, truncate))
File "/usr/hdp/2.3.4.0-3485/spark/python/lib/py4j-0.8.2.1-src.zip/py4j/java_gateway.py", line 538, in __call__
File "/usr/hdp/2.3.4.0-3485/spark/python/pyspark/sql/utils.py", line 36, in deco
return f(*a, **kw)
File "/usr/hdp/2.3.4.0-3485/spark/python/lib/py4j-0.8.2.1-src.zip/py4j/protocol.py", line 300, in get_return_value
py4j.protocol.Py4JJavaError: An error occurred while calling o7299.showString.
: org.apache.spark.SparkException: Job aborted due to stage failure: Task 0 in stage 1.0 failed 1 times, most recent failure: Lost task 0.0 in stage 1.0 (TID 365, localhost): org.apache.spark.api.python.PythonException: Traceback (most recent call last):
File "/usr/hdp/2.3.4.0-3485/spark/python/lib/pyspark.zip/pyspark/worker.py", line 98, in main
command = pickleSer._read_with_length(infile)
File "/usr/hdp/2.3.4.0-3485/spark/python/lib/pyspark.zip/pyspark/serializers.py", line 164, in _read_with_length
return self.loads(obj)
File "/usr/hdp/2.3.4.0-3485/spark/python/lib/pyspark.zip/pyspark/serializers.py", line 422, in loads
return pickle.loads(obj)
File "test2.py", line 16, in <module>
str2numUDF=F.udf(lambda s: str2num(s), t.IntegerType())
File "/usr/hdp/2.3.4.0-3485/spark/python/lib/pyspark.zip/pyspark/sql/functions.py", line 1460, in udf
return UserDefinedFunction(f, returnType)
File "/usr/hdp/2.3.4.0-3485/spark/python/lib/pyspark.zip/pyspark/sql/functions.py", line 1422, in __init__
self._judf = self._create_judf(name)
File "/usr/hdp/2.3.4.0-3485/spark/python/lib/pyspark.zip/pyspark/sql/functions.py", line 1430, in _create_judf
pickled_command, broadcast_vars, env, includes = _prepare_for_python_RDD(sc, command, self)
File "/usr/hdp/2.3.4.0-3485/spark/python/lib/pyspark.zip/pyspark/rdd.py", line 2317, in _prepare_for_python_RDD
[x._jbroadcast for x in sc._pickled_broadcast_vars],
AttributeError: 'NoneType' object has no attribute '_pickled_broadcast_vars'
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.sql.execution.BatchPythonEvaluation$$anonfun$doExecute$1.apply(python.scala:397)
at org.apache.spark.sql.execution.BatchPythonEvaluation$$anonfun$doExecute$1.apply(python.scala:362)
at org.apache.spark.rdd.RDD$$anonfun$mapPartitions$1$$anonfun$apply$17.apply(RDD.scala:710)
at org.apache.spark.rdd.RDD$$anonfun$mapPartitions$1$$anonfun$apply$17.apply(RDD.scala:710)
at org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:38)
at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:300)
at org.apache.spark.rdd.RDD.iterator(RDD.scala:264)
at org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:38)
at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:300)
at org.apache.spark.rdd.RDD.iterator(RDD.scala:264)
at org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:38)
at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:300)
at org.apache.spark.rdd.RDD.iterator(RDD.scala:264)
at org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:38)
at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:300)
at org.apache.spark.rdd.RDD.iterator(RDD.scala:264)
at org.apache.spark.scheduler.ResultTask.runTask(ResultTask.scala:66)
at org.apache.spark.scheduler.Task.run(Task.scala:88)
at org.apache.spark.executor.Executor$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.sql.execution.SparkPlan.executeTake(SparkPlan.scala:215)
at org.apache.spark.sql.execution.Limit.executeCollect(basicOperators.scala:207)
at org.apache.spark.sql.DataFrame$$anonfun$collect$1.apply(DataFrame.scala:1385)
at org.apache.spark.sql.DataFrame$$anonfun$collect$1.apply(DataFrame.scala:1385)
at org.apache.spark.sql.execution.SQLExecution$.withNewExecutionId(SQLExecution.scala:56)
at org.apache.spark.sql.DataFrame.withNewExecutionId(DataFrame.scala:1903)
at org.apache.spark.sql.DataFrame.collect(DataFrame.scala:1384)
at org.apache.spark.sql.DataFrame.head(DataFrame.scala:1314)
at org.apache.spark.sql.DataFrame.take(DataFrame.scala:1377)
at org.apache.spark.sql.DataFrame.showString(DataFrame.scala:178)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
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 "/usr/hdp/2.3.4.0-3485/spark/python/lib/pyspark.zip/pyspark/worker.py", line 98, in main
command = pickleSer._read_with_length(infile)
File "/usr/hdp/2.3.4.0-3485/spark/python/lib/pyspark.zip/pyspark/serializers.py", line 164, in _read_with_length
return self.loads(obj)
File "/usr/hdp/2.3.4.0-3485/spark/python/lib/pyspark.zip/pyspark/serializers.py", line 422, in loads
return pickle.loads(obj)
File "test2.py", line 16, in <module>
str2numUDF=F.udf(lambda s: str2num(s), t.IntegerType())
File "/usr/hdp/2.3.4.0-3485/spark/python/lib/pyspark.zip/pyspark/sql/functions.py", line 1460, in udf
return UserDefinedFunction(f, returnType)
File "/usr/hdp/2.3.4.0-3485/spark/python/lib/pyspark.zip/pyspark/sql/functions.py", line 1422, in __init__
self._judf = self._create_judf(name)
File "/usr/hdp/2.3.4.0-3485/spark/python/lib/pyspark.zip/pyspark/sql/functions.py", line 1430, in _create_judf
pickled_command, broadcast_vars, env, includes = _prepare_for_python_RDD(sc, command, self)
File "/usr/hdp/2.3.4.0-3485/spark/python/lib/pyspark.zip/pyspark/rdd.py", line 2317, in _prepare_for_python_RDD
[x._jbroadcast for x in sc._pickled_broadcast_vars],
AttributeError: 'NoneType' object has no attribute '_pickled_broadcast_vars'
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.sql.execution.BatchPythonEvaluation$$anonfun$doExecute$1.apply(python.scala:397)
at org.apache.spark.sql.execution.BatchPythonEvaluation$$anonfun$doExecute$1.apply(python.scala:362)
at org.apache.spark.rdd.RDD$$anonfun$mapPartitions$1$$anonfun$apply$17.apply(RDD.scala:710)
at org.apache.spark.rdd.RDD$$anonfun$mapPartitions$1$$anonfun$apply$17.apply(RDD.scala:710)
at org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:38)
at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:300)
at org.apache.spark.rdd.RDD.iterator(RDD.scala:264)
at org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:38)
at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:300)
at org.apache.spark.rdd.RDD.iterator(RDD.scala:264)
at org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:38)
at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:300)
at org.apache.spark.rdd.RDD.iterator(RDD.scala:264)
at org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:38)
at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:300)
at org.apache.spark.rdd.RDD.iterator(RDD.scala:264)
at org.apache.spark.scheduler.ResultTask.runTask(ResultTask.scala:66)
at org.apache.spark.scheduler.Task.run(Task.scala:88)
at org.apache.spark.executor.Executor$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
作为检查，我打开了一个干净的 shell，而不是导入模块，我只是在交互式 shell 中定义了 str2num 函数和 UDF。然后我输入了最后一个函数的内容，并进行了同样的最终检查：
df2.show()
这一次，我得到了我期待的转换后的 DataFrame。
为什么交互输入函数时它起作用，但从模块中读取它们时不起作用？我知道它正在读取模块，因为常规函数 str2num 有效。