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spark:using-python [2019/11/12 13:19]
straka 		spark:using-python [2022/12/14 12:59]
straka [Usage Examples]
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 Consider the following simple script computing 10 most frequent words of Czech Wikipedia: Consider the following simple script computing 10 most frequent words of Czech Wikipedia:
 <file python> <file python>
-(sc.textFile("/net/projects/spark-example-data/wiki-cs", 3*sc.defaultParallelism)+(sc.textFile("/lnet/troja/data/npfl118/wiki/cs/wiki.txt", 3*sc.defaultParallelism)
    .flatMap(lambda line: line.split())    .flatMap(lambda line: line.split())
    .map(lambda word: (word, 1))    .map(lambda word: (word, 1))
    .reduceByKey(lambda c1,c2: c1+c2)    .reduceByKey(lambda c1,c2: c1+c2)
-   .sortBy(lambda (word,count): count, ascending=False)+   .sortBy(lambda word_count: word_count[1], ascending=False)
    .take(10))    .take(10))
 </file> </file>
  
-  * run interactive shell using existing Spark cluster (i.e., inside ''spark-qrsh''), or start local Spark cluster using as many threads as there are cores if there is none:+  * run interactive shell using existing Spark cluster (i.e., inside ''spark-srun''), or start local Spark cluster using as many threads as there are cores if there is none:
   <file>PYSPARK_DRIVER_PYTHON=ipython3 pyspark</file>   <file>PYSPARK_DRIVER_PYTHON=ipython3 pyspark</file>
   * run interactive shell with local Spark cluster using one thread:   * run interactive shell with local Spark cluster using one thread:
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   <file>PYSPARK_DRIVER_PYTHON=ipython3 spark-qrsh 10 1G pyspark</file>   <file>PYSPARK_DRIVER_PYTHON=ipython3 spark-qrsh 10 1G pyspark</file>
  
-Note that ''PYSPARK_DRIVER_PYTHON'' variable can be left out or specified in ''.bashrc'' (or similar).+Note that ''PYSPARK_DRIVER_PYTHON'' variable can be left out or specified in ''.bashrc'' (or other configuration files).
  
  
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    .map(lambda token: (token, 1))    .map(lambda token: (token, 1))
    .reduceByKey(lambda x,y: x + y)    .reduceByKey(lambda x,y: x + y)
-   .sortBy(lambda (word,count): count, ascending=False)+   .sortBy(lambda word_count: word_count[1], ascending=False)
    .saveAsTextFile(output))    .saveAsTextFile(output))
 sc.stop() sc.stop()

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