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MapReduce, mail # user - How to import custom Python module in MapReduce job?

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How to import custom Python module in MapReduce job?
Andrei 2013-08-12, 06:50
(cross-posted from

I have a MapReduce job defined in file *main.py*, which imports module lib from
file *lib.py*. I use Hadoop Streaming to submit this job to Hadoop cluster
as follows:

hadoop jar /usr/lib/hadoop-mapreduce/hadoop-streaming.jar

    -files lib.py,main.py
    -mapper "./main.py map" -reducer "./main.py reduce"
    -input input -output output

In my understanding, this should put both main.py and lib.py into *distributed
cache folder* on each computing machine and thus make module lib available
to main. But it doesn't happen - from log file I see, that files *are
really copied* to the same directory, but main can't import lib, throwing*

Adding current directory to the path didn't work:

import sys
sys.path.append(os.path.realpath(__file__))import lib# ImportError

though, loading module manually did the trick:

import imp
lib = imp.load_source('lib', 'lib.py')

But that's not what I want. So why Python interpreter can see other .py files
in the same directory, but can't import them? Note, I have already tried
adding empty __init__.py file to the same directory without effect.
Binglin Chang 2013-08-12, 08:33
Binglin Chang 2013-08-12, 10:12