gistfile1.py

from collections import defaultdict

def splitter(lines, keyfunc, valuefunc):
    d = defaultdict(list)

    for line in lines:
        cols = line.split()
        key = keyfunc(cols)
        value = valuefunc(cols)
        d[key].append(value)

    return d


TEST_TEXT = '''
one 1 bar
two 2 baz
foo 1 bat
'''.strip()


if __name__ == '__main__':
    lines = TEST_TEXT.split('\n')

    keyfunc = lambda cols: cols[1]
    valuefunc = lambda cols: (cols[0], cols[2])

    expected = {
        '1': [('one', 'bar'), ('foo', 'bat')],
        '2': [('two', 'baz')],
    }

    d = splitter(lines, keyfunc, valuefunc)

    assert d == expected

    # works with files too
    from StringIO import StringIO
    fake_fh = StringIO(TEST_TEXT)

    d = splitter(fake_fh, keyfunc, valuefunc)

    assert d == expected

    # write splitter dictionary
    for key, values in d.items():
        with open(key, 'w') as out:
            for value in values:
                out.write(' '.join(value) + '\n')