how to control the output of reducer?

[xpjian]

hi, all:

    my case is that I want to select some matched lines from a file and print them into output file. But in the reducer , I finally "yield key, values.netxt()", it can not omit the key( in this file case, the key is the offset of the line in the file". Here is my code .

def mapper(key, value):

    import re

    if re.compile(r'\d').match(value):

        yield key, value

def reducer(key, value):

    yield key, value.next()

if __name__ == '__main__':

    import dubmo

    dubmo.run(mapper, reducer)

and my inputfile is like this:

a

1

3

d

so , I want the output file like this:

1

3

but , the above MR outputs 

1, 1

2, 3

Does anyone can help?

[Gilles]

Hi,
2 comments first:
You don't have to use a reducer if you don't need to you can run:

if __name__ == '__main__':

    import dumbo

    dumbo.run(mapper)

You can also use the identityreducer found in dumbo.lib this is an exemple of the code:
 def identityreducer(key, values):
    for value in values:   
        yield (key, value)   

This said if you want to have one line in your output per line matching your regex: use just a mapper and emit all with an empty key
If you want a unique output per distinct values that match you regex you can use this code

def mapper(key, value):

    import re

    if re.compile(r'\d').match(value):

        yield value,""