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--- spark:using-python [2014/11/10 15:17]
straka
+++ spark:using-python [2022/12/14 13:25] (current)
straka [Usage Examples]
@@ Line 8: / Line 8: @@
 <file>pyspark</file>
-Better interactive shell with code completion using ''ipython'' (installed everywhere on cluster; ask our IT if you want to have it installed on your workstations too) can be started using:
+Better interactive shell with code completion using ''ipython3'' (do `pip3 install --user ipython` if you do not have it) can be started using:
-<file>IPYTHON=1 pyspark</file>
+<file>PYSPARK_DRIVER_PYTHON=ipython3 pyspark</file>
 As described in [[running-spark-on-single-machine-or-on-cluster|Running Spark on Single Machine or on Cluster]], environmental variable ''MASTER'' specifies which Spark master to use (or whether to start a local one).
 ==== Usage Examples ====
+Consider the following simple script computing 10 most frequent words of Czech Wikipedia:
+<file python>
+(sc.textFile("/net/projects/spark-example-data/wiki-cs", 3*sc.defaultParallelism)
+   .flatMap(lambda line: line.split())
+   .map(lambda word: (word, 1))
+   .reduceByKey(lambda c1, c2: c1+c2)
+   .sortBy(lambda word_count: word_count[1], ascending=False)
+   .take(10))
+</file>
-  * run interactive shell with local Spark cluster using as many threads as there are cores:
+  * 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>IPYTHON=1 pyspark #if MASTER not defined
+  <file>PYSPARK_DRIVER_PYTHON=ipython3 pyspark</file>
-MASTER="local[*]" IPYTHON=1 pyspark #if MASTER is defined differently and must be overwritten</file>
   * run interactive shell with local Spark cluster using one thread:
-  <file>MASTER=local IPYTHON=1 pyspark</file>
+  <file>MASTER=local PYSPARK_DRIVER_PYTHON=ipython3 pyspark</file>
-  * start Spark cluster (10 machines, 1GB RAM each) on SGE and run interactive shell:
+  * start Spark cluster (10 machines, 2GB RAM each) on Slurm and run interactive shell:
-  <file>IPYTHON=1 spark-qrsh 10 1G pyspark</file>
+  <file>PYSPARK_DRIVER_PYTHON=ipython3 spark-srun 10 2G pyspark</file>
-Note that ''IPYTHON'' 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).
 ===== Running Python Spark Scripts =====
-Python Spark scripts can be started using ''spark-submit''.
+Python Spark scripts can be started using:
+<file>spark-submit</file>
+As described in [[running-spark-on-single-machine-or-on-cluster|Running Spark on Single Machine or on Cluster]], environmental variable ''MASTER'' specifies which Spark master to use (or whether to start a local one).
+==== Usage Examples ====
+Consider the following simple word-count script ''word_count.py'':
+<file python>
+#!/usr/bin/python
+import sys
+if len(sys.argv) < 3:
+    print >>sys.stderr, "Usage: %s input output" % sys.argv[0]
+    exit(1)
+input = sys.argv[1]
+output = sys.argv[2]
+from pyspark import SparkContext
+sc = SparkContext()
+(sc.textFile(input, 3*sc.defaultParallelism)
+   .flatMap(lambda line: line.split())
+   .map(lambda token: (token, 1))
+   .reduceByKey(lambda x, y: x + y)
+   .sortBy(lambda word_count: word_count[1], ascending=False)
+   .saveAsTextFile(output))
+sc.stop()
+</file>
+  * run ''word_count.py'' script inside existing Spark cluster (i.e., inside ''spark-sbatch'' or ''spark-srun''), or start local Spark cluster using as many threads as there are cores if there is none:
+  <file>spark-submit word_count.py /net/projects/spark-example-data/wiki-cs outdir</file>
+  * run ''word_count.py'' script with local Spark cluster using one thread:
+  <file>MASTER=local spark-submit word_count.py /net/projects/spark-example-data/wiki-cs outdir</file>
+  * start Spark cluster (10 machines, @GB RAM each) using Slurm and run ''word_count.py'' script:
+  <file>spark-sbatch 10 2G spark-submit word_count.py /net/projects/spark-example-data/wiki-cs outdir</file>
+===== Using Virtual Environments =====
+If you want to use specific virtual environment in your Spark job, use
+<file>PYSPARK_PYTHON=path_to_python_in_venv [pyspark|spark-submit]</file>

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