[Lucene-hadoop Wiki] Update of "PythonWordCount" by OwenOMalley

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http://wiki.apache.org/lucene-hadoop/PythonWordCount

New page:
= WordCount Example in Python =

This is the WordCount example completely translated into [http://python.org/ Python] and translated using [http://www.jython.org/Project/index.html Jython] into a Java jar file.

The program reads text files and counts how often words occur.  The input is text files and the output is text files, each line of which contains a word and the count of how often it occured, separated by a tab.

Each mapper takes a line as input and breaks it into words. It then emits a key/value pair of the word and 1. Each reducer sums the counts for each word and emits a single key/value with the word and sum.

As an optimization, the reducer is also used as a combiner on the map outputs. This reduces the amount of data sent across the network by combining each word into a single record.

To compile the example, build the Hadoop code:{{{
  ant
  cd src/examples/python
  ./compile
}}}

To run the example, the command syntax is: {{{
  ../../../bin/hadoop jar wc.jar [-m <#maps>] [-r <#reducers>] \
    <in-dir> <out-dir>
}}}