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Using Python

In order to use Spark in Python, environment has to bee set up according to Using Spark in UFAL Environment.

Starting Interactive Shell

Interactive shell can be started using:

pyspark

Better interactive shell with code completion using ipython3 (do `pip3 install –user ipython` if you do not have it) can be started using:

PYSPARK_DRIVER_PYTHON=ipython3 pyspark

As described in 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:

(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))
PYSPARK_DRIVER_PYTHON=ipython3 pyspark
MASTER=local PYSPARK_DRIVER_PYTHON=ipython3 pyspark
PYSPARK_DRIVER_PYTHON=ipython3 spark-qrsh 10 1G pyspark

Note that PYSPARK_DRIVER_PYTHON variable can be left out or specified in .bashrc (or similar).

Running Python Spark Scripts

Python Spark scripts can be started using:

spark-submit

As described in 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:

#!/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()
spark-submit word_count.py /net/projects/spark-example-data/wiki-cs outdir
MASTER=local spark-submit word_count.py /net/projects/spark-example-data/wiki-cs outdir
spark-qsub 10 1G spark-submit word_count.py /net/projects/spark-example-data/wiki-cs outdir

Using Virtual Environments

If you want to use specific virtual environment in your Spark job, use

PYSPARK_PYTHON=path_to_python_in_venv [pyspark|spark-submit]

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